## Looking at Jenrry Mejia's first start in 2013 with Pitchf/x

A few years ago, Jenrry Mejia came up as a reliever for the New York Mets. Mejia was the Mets' top pitching prospect, and it certainly seemed like a waste of his development for him to be a reliever. In addition, his results weren't quite so good. That said, his pitches were extremely promising in movement/velocity, as I noted in a pitchf/x profile on Mejia as a reliever. Then injuries and setbacks dropped Mejia in the organization such that he kind of dropped off the radar.

Until yesterday, when he pulled off the best performance of his career, striking out 7 batters, walking none, and getting a ton of ground balls. What changed? How does the stuff look? Let's take a quick look:

Figures 1 and 2: Graphs of the movement and velocity of Mejia's pitches on Friday.

Vertical Movement: the amount of inches the ball drops/"rises" as compared to how we would expect gravity to make a pitch drop. So a Fastball with Positive 10 Vertical Movement "RISES" 10 inches more than it should if gravity was the only force acting on it and a curveball with -10 Vertical Movement drops 10 inches more than a pitch thrown that is just acted on by gravity.

Horizontal Movement: The Graph is from the view of a catcher or umpire behind home plate. So a pitch that's on the left side of the graph (and has "negative horizontal movement") moves in on righties and away from lefties. A pitch that's on the right side of the graph moves in on lefites and away from righties.

Legend for this Graph and All Subsequent Graphs:
Fastballs = Red Dots
Change Ups = Yellow Dots
Sliders = Blue Dots
Curve Balls = Purple Dots

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Mejia threw four or five pitches yesterday - at least one fastball, a change-up, a curveball, and a slider. Mejia stuck yesterday to traditional pitch usage: sliders to right-handed batters (since Mejia is a righty) and change-ups to left-handed batters for the most part. It will be interesting to see how much this continues.

Mejia's primary pitch is his fastball, colored in red in the above graph.* It's the thing that makes him a very unique pitch. See, a traditional four-seam fastball breaks toward a same-handed batter - so a righty pitcher will throw a fastball that breaks about 7 inches toward a right-handed batter. Now here's the key: the batter doesn't see 7 inches of break. Why? Because the 7 inches of break actually result in a fastball roughly heading toward the plate head on, so the pitch looks straight to a batter.

*In the past, Mejia has thrown a four-seam fastball and a two-seam fastball. It's not clear if Mejia has thrown a two-seamer in that start - there's like 1 pitch that looks like a two-seam fastball and some of his change-ups border fastballs in velocity. For now, I'm acting as if the two-seamer hasn't been shown yet.

Mejia's fastball however doesn't do this: it actually breaks a half an inch AWAY from right-handed batters, the opposite direction as a classic fastball. In other words, the pitch behaves more like a cut fastball (cutter), except with a LARGE amount of cut and at an above average velocity for a cut-fastball (above 93 MPH on average, while most cutters are around 90). The result of this is that the pitch approaches the plate on a big angle, not head-on, like a slider. This can result in the pitch being harder to make good contact on (think Mariano Rivera, albeit without as great control) as well as some weird splits.

In addition, Mejia's four-seam fastball, like a cut-fastball, has a good amount of "sink." In reality, the pitch has just under 5 inches of "rise" on average, which on a 93+ MPH fastball essentially translates to make the pitch a "sinking" fastball (although, as a cutting pitch instead of a two-seamer, it moves very differently). As a result, the pitch should be a great pitch at getting ground balls.

Mejia's change-up is his primary secondary pitch vs lefties, if that last start is anything to go on (and this fits his pitching strategy in the past, so I'd bet it is). The pitch essentially acts like a traditional two-seam fastball in movement, with okay tail and sink at around 87 MPH on average. Of course, because Mejia's primary fastball has cut instead of tail, this means that the tailing action on this pitch probably throws batters used to his fastball's cut for a loop. And Mejia's change-up was decently effective in his first start, for what that's worth.

On the other hand, the fact that Mejia's change-up has such different movement than his fastball makes it so that his change-up might no't really serve as a traditional change-up - which has similar movement to a fastball but just has slower velocity and maybe a bit more drop. It remains to be seen how that'll play out among Mejia's results.

This brings us to Mejia's next pitch, his slider. This appears to be a BRAND NEW PITCH. As noted by myself on twitter, and illustrated brilliantly by Carson Cistulli in the image below, Mejia did not showcase this pitch last year or in his appearances a few years back as a reliever:

This pitch is similar to Harvey/Wheeler's slider in movement, with about 1.2 inches of horizontal break away from righties and about 2 inches of rise on average, and averaging roughly 85 MPH. But how this pitch fits in with Mejia's repertoire is VERY different from Harvey or Wheeler. Because unlike those guys, Mejia's slider essentially has the same horizontal break as his FASTBALL, but just more SINK and less velocity. In other words, despite being used against same-handed batters, the pitch acts like a CHANGE-UP, in how it plays off the fastball.

By the way, this pitch was the KEY to Mejia's success on Friday. 11/24 Sliders got swinging strikes, which are the key to striking out batters, and that's an incredible rate. Batters swung at 3/4 of his sliders, but whiffed on nearly 2/3 of those they swung at. And 4/6 put into play were hit on the ground. Devastating. And these are results we'd expect to see from a change-up btw, which is usually the best pitch at getting swinging strikes.

It's this slider that makes Mejia so interesting to watch from this point forward. Is it a flash in the pan? Or is it something real he's discovered? Because it gives Mejia something he never had, a real strikeout pitch.

Finally, Mejia also has a curveball, but he only threw it 8 times on Friday. Mejia's curveball has generally been a sweeping curveball with a bunch of vertical drop and a decent velocity of around 80 MPH. The curve's movement varied a bit on Friday, so it's unclear how it has changed since Mejia's last appearance, but it appears to have more horizontal break and less vertical drop. It remains to be seen how much Mejia plans to throw this pitch given the introduction of the slider as another breaking ball.

Conclusion:

Three Young Met Pitchers have come up as starters recently with newish sliders - Harvey, Wheeler, and now Mejia. It makes one wonder whether the pitch has become a focus of the organization. That said, this slider, when combined with Mejia's crazy cutting fastball, makes Mejia a pitcher with real promise, such that we thought about a few years ago. It's possible that that last start was an utter fluke, and the slider will turn out to be a bust.

But it could also be the thing that catapults Mejia from that guy with weird moving pitches to that guy whose pitches confuse the hell out of batters and cause them tons of trouble. Here's hoping for the latter.

This FanPost was contributed by a member of the community and was not subject to any vetting or approval process.