Before I start, I need to confess: I'm not an expert in hitting mechanics. I usually study catcher defense, but I wanted to look at something new. Since I already had a bunch of game footage with Plawecki, I figured I would try to find out why he has struggled at the plate in the majors so far. Because I don't know a whole lot about hitting, I've gathered opinions from various scouts and coaches to put this post together.
Things I'll be talking about:
-his front foot/timing
-why his strikeout rate has increased
-his new vulnerability against the fastball
I put a summary at the very end, so if you don't want to read this incredibly long post, you can skip to that. But I would recommend at least glancing over the gifs so you can visualize what I'm talking about.
I'll start off with my favorite swing of his in the majors, from April 30, 2015. Inner-half 95 mph fastball, and he inside-outs it to the opposite gap. That is hard to do.
Plawecki has been in pro ball for 4.5 seasons, and his swing/stance has gone through three different phases in that time.
From left to right:
- Phase 1 (July 2, 2012 Low-A, home run). This is the swing he had in college. He used this from 2012-early 2013: Low-A, Single-A. The only exception is that one-handed follow through, which he didn't completely get rid of until 2014.
- Phase 2 (May 5, 2015 MLB, double). This is the swing you saw in 2015. He used this from late 2013 to 2015: High-A, Double-A, Triple-A, MLB rookie season.
- Phase 3 (June 9, 2016 MLB, single). This is the swing you saw in 2016.
He got a pretty big overhaul to his swing last season. They made his stance wide and open, they lowered his hands, they shortened his stride, they made him crouched instead of straight up and down, etc.
With every new change comes an adjustment period. They introduced mechanics that he's basically never used in his life, so you can imagine it has to take some time to get used to them, and those changes can sometimes cause issues.
In 2015, most of his batted ball numbers were close to league average. I know the results didn't show it, but he got a little unlucky that year. (That's a long article, so if you don't want to read it, basically Plawecki was the fourth "unluckiest slugger" in 2015. His slugging percentage should've been 102 points higher than it was and his ISO should've been 54 points higher based on how many balls he barreled. So he "should've" had a .398 slugging percentage and a .131 ISO in 2015. It uses Statcast's new "Barrels" stat, which is based on exit velocity and launch angle.) These numbers all went in the wrong direction in 2016.
Batted ball stats:
|Plawecki's 2015||2015 league average||Plawecki's 2016||2016 league average|
|Plawecki's average exit velocity||89.0 mph||84.2 mph|
|League average exit velocity||88.5 mph||89.1 mph|
|Plawecki's peak exit velocity||112.8 mph||107.8 mph|
It's obvious that something was fundamentally altered. None of these numbers were even close to being the same. I'm going to go over a few of the changes they made and the flaws that got introduced. (Not claiming the changes they made were bad.)
First thing I'll mention briefly is that Plawecki does this thing where he drops his hands/bat down before he swings. You may have heard this referred to as a hitch. This is often just the hitter's timing mechanism. You can see that this hitch was pretty big in Phase 2, so they cut it down last season.
His front foot/timing
Left to right:
- Phase 1 (May 26, 2012 Purdue junior year, home run)
- Phase 2 (April 30, 2015 MLB, double)
- Phase 3 (May 17, 2016 MLB, single)
I'd like to point out his hitch/hand movement for a second. Very minimal movement in Phase 3. Also notice the difference in the path that his hands are taking.
In Phase 1, he had a toe tap. Some people call this a double stride, because he steps back slightly and then steps forward. Plawecki's favorite player as a kid was Sammy Sosa, and that's exactly who he picked it up from. Not a whole lot of players do this anymore. I've been told it's because it's difficult to maintain—you often need to have near-elite control of your bat and body to use it. Plawecki's stride here went from the front of home plate to just beyond it, about the length of his foot.
In Phase 2, his toe tap morphed into more of a half/mini toe tap. His foot often didn't entirely leave the ground:
If it did, it barely left the ground. This time he didn't step back like he did in Phase 1, and that's why he starts with a narrower stance. His stride here was a bit more than the length of home plate. That's a pretty long stride. (Not that there's anything wrong with a long stride.)
In Phase 3, they eliminated the toe tap and it became more like a small leg kick or a leg lift. His stride here is the shortest of the three.
I tried to make the gif so that he started his swing process at the same time in all three phases. Phases 1 and 2 sync up nicely. Phase 3 is a different story. He's planting his foot earlier (by about six frames, which is a lot) and therefore starting his swing earlier. Why? Because he's missing that toe tap. While he was tapping his toe in Phases 1 and 2, his leg was already striding in Phase 3. By the time he plants his foot in Phase 3, Phases 1 and 2 are still striding.
His swing process was shorter without the toe tap, but he didn't properly compensate for that. He still started his swing process at about the same time as he did before. As a result, look at where he's making contact with the ball in Phase 3. You can sort of see him try to hold back because he realizes he's too early, but that's not a great idea. If you stop after your foot is planted, you're gonna lose your momentum, which kills your bat speed. And you can tell his bat was slower. All three swings are finishing at approximately the same time, even though he started earlier in Phase 3.
As far as his stride contributing to this, I've heard it both ways, which tends to be the case when it comes to hitting mechanics. I've heard that the shorter stride is making the issue worse, but I've also heard that the shorter stride is supposed to help fix this. To me, it seems like the short stride is just exacerbating the problem. So I don't know, make your own conclusion, I guess.
From a different angle, to help illustrate how much earlier he was planting his heel in 2016:
On the left: July 4, 2015 (double to right-center field)
On the right: June 9, 2016 (grounded foul to the left side)
Both pitches were the same speed in the same location. I'm sure he can eventually live without the toe tap, but he's gotta stay back longer or slow something down if he's gonna skip it.
More on his toe tap
I couldn't find the reason why they removed his toe tap, but I did find out that he'd had a toe tap since he was eight years old. They eliminated something he's been doing for 17 years. And they eliminated it at the major league level. Sounds like a brilliant idea :|
Most of the adjustments they made to Plawecki's swing/stance happened in the offseason. As far as I know, the only two things that they adjusted during the season was his hitch and this toe tap. His hitch was all over the place. First they tried to get rid of it entirely, but getting rid of someone's timing mechanism probably isn't gonna work out the way you want it to. It ended up fluctuating in magnitude throughout the season.
But anyway, the toe tap got changed early in the season. May 1, to be exact. I can tell, because he's both toe tapping and leg lifting in this game. The toe tap was gone by May 2nd. Pretty impressive that he was able to drop something he's been doing for 17 years that quickly. Let's see what that did to his offense...
He went hitless on May 2 and May 3. But from May 5 to May 14, he went 8-for-28 with four doubles and a home run: .286/.333/.536 (.869 OPS).
Not bad, right? But you know what they say: don't scout the stat line. I watched all eight of these hits, and you know what I saw? Curveball, fastball, slider, slider, changeup, fastball, slider, slider.
If you watched him in 2015, you would know how vulnerable he was against the slider. So you might be thinking, "well he got four hits off sliders, that's good." Yeah that's nice, but those fastballs were 90 mph. Remember what I said about his bat speed dying?
Last season, he went 1-for-14 (.071) with no XBHs against 95+ mph velocity. That was dead last among Mets hitters. Even if you lower the threshold to 93+, he was still last on the team.
One of the things that distinguished Plawecki his rookie season and in the minor leagues was his ability to hit high velocity. He feasted on fastballs. In 2015, he had the third highest batting average (.296, 8-for-27) and the third highest slugging (.481) on the team against 95+, both behind Daniel Murphy and Yoenis Cespedes.
For reference, some career batting average and slugging percentage against 95+ mph:
|Jay Bruce||.243 (72-for-296)||.422|
|Curtis Granderson||.222 (77-for-347)||.403|
|Neil Walker||.217 (48-for-221)||.348|
|Asdrubal Cabrera||.202 (67-for-332)||.322|
|Michael Conforto||.194 (13-for-67)||.299|
|Wilmer Flores||.189 (21-for-111)||.234|
|Travis d'Arnaud||.179 (17-for-95)||.263|
|Rene Rivera||.169 (14-for-83)||.217|
There are some good hitters on that list (...and some not-so-good hitters). It's no secret that it's difficult to hit high velocity. Though it was a small sample, Plawecki hitting 95+ at a .296 clip as a rookie catcher was a great sign. Actually, if you only look at Healthy Plawecki, he hit .375 (6-for-16) against 95+, which would've been best on the team by almost 40 points, and a .625 slugging percentage, which would've been second best behind Cespedes.
He clearly lost this ability last season. When trying to fix something in a hitter, you definitely don't want to get them away from what they did well. Unfortunately that happened to Plawecki, in more ways than one.
(also referred to as drifting or leaking)
On the top: April 30, 2015 (double)
On the bottom: May 17, 2016 (single)
Red line: tracking head movement
Blue line: tracking hip movement
Ideally, neither his head nor his hips should be moving around too much. Plawecki's 2015 is fine. But his hips are sliding much more in 2016 and as a result, his head drifts forward, which makes it hard to keep your eye on the ball.
This hip slide can affect a hitter's power because they're shifting too much weight forward and a lot of the energy they built up in their lower body leaks out. If you look at Plawecki's front leg, you can see it's bending a bit more in 2016 because of that extra weight he shifted forward during the slide. Since you don't wanna be making contact on a bent front leg, he's pushing all that weight back and that's probably why you see his back leg coming off the ground more than it did before.
Another thing that the hip slide can do is make the hitter vulnerable to the inside pitch. Anyone who has followed Plawecki's minor league career should know that he was a kid who would crush you on inside pitches. His hands were so quick inside.
In 2015, Healthy Plawecki had a .469 slugging percentage on inside pitches, with a homer and four doubles. (See also: that clip I posted above.)
In 2016, he had a .250 slugging percentage. .250! He had zero extra base hits on inside pitches. He popped out four times in 28 at-bats and pounded a whole bunch of pitches into the ground. And he kept swinging at that inside pitch because why wouldn't he? It used to be his strength.
I have a couple different theories as to why he's hip sliding. One is that it developed as a result of them modifying his toe tap and stride. He was getting his front foot down way too early and maybe he would accidentally slide forward trying to make sure he made contact with the pitch.
My other theory has to do with the way he's planting his foot:
2015 on the left, 2016 on the right. (Both home runs, if anyone's curious.)
It took him longer to go from toe touch to heel plant in 2016. In 2015, he was basically planting his whole foot at the same time. Planting his heel triggers hip rotation and therefore prevents any slide. So that extra time it's taking him to plant his heel is when he's hip sliding. It seems small, but it's a very damaging flaw.
I think/hope they already knew about his hip slide. I remember hearing Howie during a game in June talking about how Terry (of all people) was working with Plawecki on something to do with his hips. Didn't mention specifically what it was, he was just commenting on the fact that Terry was working with him hands-on, the way a high school coach would.
But this isn't easy to fix in the middle of a season. It's a tiny flaw, visually speaking. You usually need video to see it, which means if none of the coaches can see it happen in real time, Plawecki can't get feedback during the game on whether or not he's transferring his weight correctly. It also doesn't help if you're not playing that often, like he was, sitting on the bench every other game. You can swing with the right mechanics all you want in the cage, but translating that in-game can be very difficult, especially if you're young/inexperienced/anxious at the plate.
That being said, after he came back from the minors:
(October 2, 2016, double to right-center field)
He's not planting his heel quite as fast as he was in 2015, but it's not nearly as slow as pre-demotion 2016. If I'm right about his foot plant being the culprit of his hip slide, then that means it was corrected while he was in the minors. But I can't say for sure that the issue is gone, because I can't tell if he's sliding without a good side view. He had all of eight plate appearances after he came back from the minors, which is not a meaningful sample size by any means, but his average exit velocity in those eight plate appearances was 92.4 mph, he hit at least 104 mph four times, and his hard% was 33.3%, up from 18.3% earlier in the season, a 15% increase.
Can't make any conclusions because of that minuscule sample size, but those are all good signs and hopefully an indicator that the sliding was corrected by the end of last season.
Quote from Plawecki in 2013:
"I'm just making sure my hands are on time and I'm in sync with my lower half. When I get in trouble is when I start lunging. I need to let the ball travel, let it come to me. I get too overanxious. I'm trying to limit that."
This was something he was still working on as late as 2014. He never got the chance to completely fix this before he came up to the majors. So once he was in the majors, facing tougher pitchers, it just got worse and worse and all the progress he made was gone.
On the left: April 13, 2016 (swing and miss)
On the right: May 7, 2016 (double)
Those are both hanging sliders. Nothing wrong with the one on the right. The one on the left is the most severe case of lunging that I saw from Plawecki out of all the swings I looked at. You can see how out-of-sync his lower body is with his upper body.
Here's what lunging looks like from the side:
That pitch was a curveball (ground ball single). Note the bent front leg at the point of contact, the bad hip slide, and the pause in the middle of his swing.
I don't think I need to explain why lunging is bad, but I will mention that hip slide can make you more prone to it. I wouldn't expect a hitter to never, ever lunge. It actually happens quite a bit. The problem with Plawecki (in the majors) was that he would almost always lunge. I watched all 34 swings he's taken against the curveball in his young MLB career and he lunged in 27 of them (79%), often very badly. And he knows he lunges, so what he would do is he would take the curveball. He wouldn't even bother swinging at it. I mean, he's seen almost 200 curveballs in his MLB career and has only swung at 34 of them. Clearly he hasn't been offering at that pitch. This becomes a problem when you want to eventually learn how to stop lunging during games and/or the pitcher drops in a curve for a strike.
This was not this big an issue while he was in the minors. If it was, he wouldn't have blown through five different levels in 2.5 seasons. I've watched tons of minor league footage of him, and not only was he not lunging nearly as often, he was also getting plenty of hits off breaking balls. Which is why I think most of this is just him being an overanxious youngster in the majors, and he needs to relax. I know "relax" isn't helpful advice, but it's true.
2015: lunged at 16 out of 18 curveballs (88.9%)
2016: lunged at 11 out of 16 curveballs (68.8%)
Around mid-May 2016 he started lunging much less. He wasn't able to square up the curveball yet, but lunging less is a good step forward.
August 22, 2016:
That was a line drive double. He's getting there.
Why his strikeout rate has increased
Plawecki struck out 29 times in 746 plate appearances in college, a 3.9% strikeout rate. The year he was drafted, he struck out eight times in 265 plate appearances, a 3.0 K%. Needless to say, he didn't strike out much. He maintained that talent in the minor leagues, with a 10.6 K% in 303 games (133 strikeouts in 1255 plate appearances) before he was called up. Every scouting report on him out there mentioned his strikeout rate/contact ability in some way shape or form.
But of course it wasn't just his strikeout rate that made him a prospect. There are plenty of low strikeout hitters out there, but a lot of them slap the ball in play and never walk. What made Plawecki a prospect (aside from his position) wasn't just his elite strikeout rate, he also walked at an average rate, drove the ball to all fields, and hit for moderate power.
I'm not a huge fan of comps because of how different every player is. But sometimes I can't help but use them as a very rough guide for progress/development. The closest hitter comp that I've had for Plawecki over the years has always been Daniel Murphy. The human version of Murphy, not the 2016 one.
Minor league numbers through Double-A (Murphy skipped Triple-A, so I had to leave that out):
Just for fun, some of their counting stats:
|# of games||doubles||triples||home runs||RBI|
Their minor league numbers are as close as you could possibly get. They had very similar profiles: high batting average, average walk rate, elite strikeout rate, doubles/gap-to-gap power. Plawecki had been projected to have 30-40 doubles and 10-15 home runs in a full season. Which is basically what Murphy has done in the majors.
Murphy so far makes more contact than Plawecki does. But it's hard to say if the rate of contact Plawecki makes now is what he's actually capable of, considering he was ill in 2015 and had mechanical issues in 2016. It would be a lot more helpful if minor league numbers had contact stats. :/
Something interesting I found, Murphy in his rookie season:
151 plate appearances, 11.9 BB%, 18.5 K%
And Plawecki last season:
151 plate appearances, 11.3 BB%, 21.9 K%
Neither of these guys are known for high walk, high strikeout rates, so seeing them both put up a high BB% and relatively high K% early in their major league career (and oddly enough, with the same number of plate appearances) is a funny coincidence.
I don't know, maybe it's still too early. Maybe Plawecki's walk and strikeout rates will go to normal pretty soon. Is it fair to use his rookie season, when he was rushed to the majors and dealing with illness? If not, that leaves me with 151 plate appearances his sophomore season to analyze. That's not enough.
Still, I am a little puzzled by his inflated strikeout rate. I rarely see hitters go from elite to below average.
Sick Plawecki vs. Healthy Plawecki
I'm sure everyone remembers that Plawecki was sick in 2015, with dizziness and double vision that (unsurprisingly) destroyed his strike zone knowledge and pitch recognition.
I made June 15, 2015 the cutoff for Sick Plawecki and am assuming that his pitch recognition magically came back in its entirety after this date, which is probably a bad assumption because he needed surgery in the offseason to fully recover. So just keep in mind these are rough numbers.
These numbers include 2016:
Apparently it's hard to have good plate discipline when your head is spinning. Those numbers from Healthy Plawecki are around or better than league average. But he wasn't known for having an average K rate. He had an elite K rate. What happened to it?
The easy answer
The easy answer is that he's probably not swinging enough. He's getting caught looking much more often than he did in the minors.
Minors: 32 strikeouts looking / 1,489 PA = 2.1% strikeouts looking (league average is a little over 5%)
Majors: 29 strikeouts looking / 409 PA = 7.1% strikeouts looking
40% of all his strikeouts while he was sick were looking. But even when healthy, he hasn't shown an improvement in this area in the majors yet:
2015: 18 strikeouts looking / 258 PA = 7.0%
2016: 11 strikeouts looking / 151 PA = 7.3%
Here's the most bizarre part: In the minors last season, he struck out looking once in 207 plate appearances (0.5%). ONCE! What the hell? And he ended up with a sparkling 9.2 K%.
My guess as to what's going on here has to do with batting order. You know how, if you're batting before the pitcher, your job is to get on base to clear the pitcher? Well, he might've taken that to an extreme and is using an approach that is far too passive. In the minors, his most common positions in the batting order were cleanup (124 games) and 5th (75 games). He was a middle of the order hitter and his job was to drive in runs, so he swung. In the majors, he may be looking to walk more than he should, so he's taking a bunch of close pitches and getting called out on them.
I don't exactly know what his K rate is when he's batting in front of the pitcher vs. not batting in front of the pitcher, but taking a quick glance at his splits:
|Batting anywhere else in the lineup||18%||7%|
My other guess has to do with his situational approach, and it kind of ties into what I said above. Out of his 11 strikeouts looking in 2016, nine of them were with the bases empty. He has a very different approach with the bases empty than he does with runners in scoring position, and it shows in his career splits:
Bases empty: .194/.244/.275 (.519 OPS)
Runners in scoring position: .269/.368/.359 (.727 OPS)
The irony is that him being more patient with the bases empty in an attempt to get on base has resulted in the opposite.
There's a very simple fix to an inflated strikeout looking rate. Just swing more. Be more aggressive. His contact% and swinging strike% are both better than average (even including Sick Plaw), so he shouldn't be worrying about swinging and missing.
It would be nice if "swing more" was enough to cut his K rate in half, but it's never that simple.
Minors: 124 swinging strikeouts / 1489 PA = 8.3% swinging Ks
Majors: 64 swinging strikeouts / 409 PA = 15.6% swinging Ks
-2015: 42 swinging strikeouts / 258 PA = 16.3%
-2016: 22 swinging strikeouts / 151 PA = 14.6%
I can tell why this has increased without even looking at the stats. The slider has been the bane of his existence. Without the slider, his MLB swinging K rate would drop by over 5%. He keeps trying to pull this pitch, which he really shouldn't be doing.
He's getting better, though. 16.3% down to 14.6%. Yay, progress!
His new vulnerability against the fastball
I know this headline sounds terrible, but he's not doomed or anything. This is just a side effect of his mechanical issues. I've already talked a bit about how his ability to hit high velocity was affected (probably because of diminished bat speed). I wanted to go into more detail about what he was doing against the fastball.
When swinging at a fastball (4-seam/2-seam):
|League average||.293||.470||89.9 mph|
|2015 Healthy Plaw||.321 (27-for-84)||.464 (2 HR, 6 doubles)||93.3 mph|
|2015 Sick Plaw||.192 (5-for-26)||.385 (1 HR, 2 doubles)||90.5 mph|
|2016 Plaw||.222 (12-for-54)||.278 (0 HR, 3 doubles)||84.8 mph|
When a dizzy Plawecki can hit the ball harder than 2016 Plawecki, something's wrong. (On another note, I never realized that Sick Plawecki's exit velocity was higher than average, but his batting average was 100 points lower than average. Now that's some unfortunate luck.)
Here are all the fastballs he's swung at (swung and missed, fouled, or put in play):
He covered the entire plate very nicely in 2015 and was pretty disciplined. But in 2016, he chased the fastball outside the strike zone more often and appeared to neglect down/away and the outer part of the strike zone.
Let's look at only the fastballs he's put in play:
That's a lot of white space middle-away in 2016. I wonder what he was doing with all those fastballs on the outer half last season...
Looks like he was either taking them for called strikes or fouling them off. He swung at an outer half fastball 35 times and only managed to put it in play six times. He had 25 foul balls. Think about that. 25 foul balls in 35 swings. That's a 71% foul ball rate, which is absurd. And out of all those outside fastballs he got, he managed one hit.
Here's what he did with those outer half fastballs in 2015:
There's 10 hits sprinkled in there (a lot of them down/away, ironically enough), including five lineouts. He put an outer half fastball in play 32 times with 33 foul balls out of 84 total swings (39% foul ball rate).
I'd expect this problem to be resolved once he fixes his timing/sliding issues.
One last thing
The only possibility that I haven't gone over yet is injury, and it's because I can't confirm that he was injured. Sometimes if a player starts swinging too early, it could be because they're overcompensating for their injury. I don't wanna start any rumors, but I've heard some quiet speculation that he was dealing with some type of right arm/shoulder injury.
I believe what prompted the chatter (besides the fact that he inexplicably started bouncing every single throw to second base) was swings like this:
This happened late July last season. I only bothered to make three gifs, but I have at least eight different swings of him doing the same thing, in consecutive at-bats, in the same series. You guys know what his normal follow through looks like, and it's definitely not that. It wasn't like his old one-handed follow through either. It's like he was unable to swing without losing his grip. I also don't think it's normal to bonk yourself in the head with your own backswing. It didn't happen again after this series, so hopefully whatever the hell that was wasn't that serious.
One of the possibilities I heard was dead arm/tired arm, which is a pretty good guess. Definitely wouldn't be the first time he's suffered from that. But again, I can't confirm injury, so take this with a grain of salt.
Plawecki's issues are timing, hip slide, and lunging. They're fixable with basically the same piece of general advice: slow down, stay back, and let the ball travel. Timing and hip slide were not issues for him prior to 2016. (Well, timing is usually a battle for everyone, but it wasn't this big a problem for Plaw.) They completely overhauled his swing and stance last season, which likely introduced these new flaws. That doesn't mean the changes they made were bad, but it's gonna take some time to get used to them.
Unfortunately Plawecki fell victim to what you hope to avoid: not compromising what he does well while trying to fix something else. These flaws turned his strengths into vulnerabilities. He went from being one of the best high velocity hitters on the Mets in 2015 (when healthy: .375 batting average—best on the team, and .625 slugging percenatage—second best on the team), to the worst (.071 batting average and .071 slugging percentage). He went from loving the inside pitch (.469 slugging percentage), to suddenly being incapable of hitting it (.250 slugging percentage).
Timing: he's putting his front foot down too early. So he swings too early and/or he's stopping his swing after his front foot is down in an attempt to stay back, but all that does is kill your bat speed. They cut down his hitch, eliminated his toe tap, and shortened his stride last season. All of these adjustments, individually, speeds up/shortens the process of his swing. Changing all three at around same time may have caused a snowball effect. He's never really had a swing like this before (he'd had a toe tap since he was eight years old), so he probably had trouble figuring out how long to stay back with these new mechanics. He's gotta slow down. I'd rather he swing late and foul it to the first base dugout than swing early and bounce it to the left side.
Being overanxious can also make this issue worse. It's possible he's afraid of being late. If he is, he needs to stop thinking that. Even if he plants his foot late, his hands and bat are more than quick enough to compensate. I mean, he can inside-out 95 mph on the inner half to the opposite gap. That's not easy to do. I don't see many hitters capable of doing that, but he can do it. I trust his ability, and I hope he does too.
One thing I did notice while he was in the minors last season was that for the first few weeks down there, he was hitting damn near everything to right field. Which is a great approach to take if you're having timing issues or trouble swinging too early.
Hip slide: his hips are sliding forward too much after he plants his toe, causing improper weight shift. It kills power because your lower body momentum/energy leaks out when you slide. I'd never seen him hip sliding before last season. My best theory behind the cause is that they changed how he plants his foot. Before, he planted his heel immediately after planting his toe. When they changed him, it took him longer to go from toe touch to heel plant and that extra time is when he's sliding. It looks and sounds like a tiny flaw, but it's quite destructive.
It's possible this got corrected while he was in the minors, because in Sept/Oct, he was planting his foot closer to the way he did in the past and hit the ball hard (at least 104 mph exit velocity) four times in his eight plate appearances. So hopefully this issue is gone.
Lunging: he's lunging forward and reaching out for breaking balls, which causes poor contact. This is something he's been working on for the past couple of seasons. Unfortunately he lost all the progress he made when he was forced into the majors too early and the lunging went from a small, occasional problem to a constant problem. He made pretty good progress in this area last season.
His strikeout rate has blown up in the majors because he's taking too many called third strikes and because the slider is kicking his butt (but he's getting better). Keep improving against the slider and be more aggressive. If he does those things, I would expect his K rate to go down.
It's also possible he was injured, but I can't confirm. A combination of him suddenly bouncing every single throw and a bizarre series of swings in July sparked this speculation.
Feel free to ask questions. About anything—Plawecki, catcher defense, or hitting. I don't have much knowledge about hitting, but I'll try to answer those questions as best I can.