Investigating Dave Hudgens, Part 1: Plate Discipline Stats

On the second to last day of the season, Terry Collins was re-upped. One of his first proclamations was that pitching coach Dan Warthen would be back for another year. Perhaps he should have started with Dave Hudgens, as the hitting coach has made quite an impact in just one year with the team.

In an effort to really suss out Hudgens' effect on the lineup, we'll start a multi-part series on the subject. First we'll revisit the key players that put up a significant number of at-bats both last year and this year. By investigating the change in their approach at the plate -- their advanced plate discipline stats -- we can see if Hudgens' philosophy took hold. Then we'll take a look at the heat maps for those key players and see if the hitting coach shrunk any holes in any swings. Last, we'll focus on the future and what advice we might give each player in order to hone their craft.

The players have to actually swing the bats, and they have to have the talent to make contact. But a hitting coach can help them understand how best to decide when to swing that bat in order to make contact more likely. Looking at the results -- runs, RBI, hits, doubles, home runs -- might ignore any progress being made at the plate.

So instead, let's today look at how some key players fared in the plate discipline statistics. Good process begets good results if given a large enough sample. Did the Mets show good process this year?

Another way of saying that things like home runs and RBI are not great numbers to use when predicting the future is saying that those numbers are not strongly correlated from year to year. For example, a players' slugging percentage is only correlated to his next year slugging percentage at the .63 level. His contact percentage, on the other hand, has a year-to-year correlation of .90. That suggests that a whole lot of luck goes into the first, and a whole lot of skill goes into the second. (See Bill Petti's great post about year-to-year correlations of hitters' stats to see more on the subject.)

In the chart below, there are a few wrinkles that won't be immediately obvious. There have been complaints about the zone-based discipline statistics on FanGraphs in the past. It's true that the league average has changed some in the past, and that the stats may not be perfect. By tying each player's statistics to the league average, as we have here, we hope to avoid some of those issues. Angel Pagan was 9.2% worse than the league average (29.3%) in 2010, when he swung at 32% of pitches outside the zone. In 2011, he swung at 4.2% better than the league average (30.6%) when he swung at 29.3% outside the zone. That should explain how to read the tables.

Also, we used color-coding to emphasize positive change in a meaningful statistic that has strong year-to-year correlation. In other words, swing percentage (swing%) and contact outside the zone (O-Contact%) are not color-coded because it's not completely clear that more (or even less) is better. For some batters, swinging more could be good. Some players make solid contact outside the zone, but mostly that sort of contact is weak. First-Strike% seems to be out of the hands of the batters -- it's only correlated .56 year-to-year.

But swinging outside the zone? It's bad. And swinging inside the zone and making contact there? It's usually good. And those numbers usually correlate well year-to-year. So that's where we'll focus.

You can immediately see Hudgens' impact. That's a 10% change in O-Swing%, and almost every key player swung at fewer pitches outside the zone with their new hitting coach. Jose Reyes was the lone below-average player seen through this lens, but he obviously is elite when it comes to making contact. Still, it's interesting that Reyes was the only player here that didn't improve his ability to avoid swinging at pitches outside the zone or add more swings inside the zone.

That's probably Hudgens' greatest impact. Players are swinging less at bad pitches outside the zone.

They are swinging less in general, and it would be great to see players swing more at pitches inside the zone, but it's only been a year. If year one allows them to swing at fewer balls outside the zone, and year two gets them to focus on swinging at good pitches in the zone, he'll get another feather in his cap. Also, not all pitches within the zone are great pitches -- but most pitches outside the zone are bad ideas. So if they swing less at pitches in the zone but make more contact, it could still be seen as a positive.

Let's look at their contact percentage numbers to fill in the rest of the picture. Hudgens may not have a ton of impact here, but it does help us see if the better approach is leading to better contact.

Well, no matter how you slice it, the Mets are making more contact in Hudgens' reign. Most players made more contact in the zone, and a particular success story was David Wright, who changed the sign on his work in the zone. For a guy that has struggled with strikeouts some, it's great to see him making more contact inside the zone. Look how many fewer swinging strikes Wright had in 2011 -- that's a swing from weakness to strength. Jason Bay also made some similar progress, but he has a ways to go.

Ruben Tejada is an interesting example. Hudgens has worked closely with Tejada in an effort to emphasize patience. Tejada has swung at more pitches outside the zone, which would seem like a bad thing, but he's still better than average in that facet of his game. And part of knowing the zone is knowing when to swing at pitches, and Tejada has swung at more pitches within the zone. And made more contact there. Tejada had a little bit of luck working against him, probably.  His first strike percentage went up -- perhaps because pitchers knew his best skill at the plate was his patience and were challenging him, or perhaps because of the vagaries of the strike zone from umpire to umpire. Either way, it seems he's still a work in progress and there are positives in his 2011 plate discipline numbers.

In the end, the Mets had the best swinging strike rate in the National League in 2011. That was a five-slot improvement since 2010, too. They swung less at pitches outside the zone, and made more contact inside the zone.

Score one (or two, or three) for Dave Hudgens.