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Two New Hitter Evaluation Tools

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Not all contact is created the same

Cincinnati Reds v St Louis Cardinals Photo by Dilip Vishwanat/Getty Images

It’s been a slow time for baseball analysis and for good reason. Writers everywhere are doing the best they can but it’s clearly limited with no current baseball to discuss. For there will be no launch angle updates for little Bart, no new spin rate data for little Lisa. Maybe little Homer will still get his Cajun sausage but he won’t be doing it at a ballpark concession stand anytime soon. Fortunately, there was a lot of great analysis coming out just before the quarantine and a few folks are still pushing forward. It’s because of that vein of analysis that I can talk about two new tools to help evaluate hitters today, and how it relates to the Cardinals. Specifically, I’m referring to Alex Chamberlain’s research on launch angle tightness and Jeff Zimmerman’s (and Ben Clemens’) research on average hard hit difference.

First, let’s look at Chamberlain’s work. He looked a great deal at “launch angle tightness”- the size of the standard deviation in a hitter’s launch angles. He gave a preview of his findings on Twitter a few weeks before Christmas:

Then he followed up with an article the next day. The less variance a hitter has in his launch angles, the more likely he is to have a higher batting average on balls in play, and (to a lesser extent) a more repeatable exit velocity.

Launch angle tightness (henceforth referred to as StDev(LA)) makes for good shorthand for bat control and a reasonable gauge for a player’s hit tool. Chamberlain also postulates that an increase in StDev(LA) may be a clue for either age-related decline or injury, though more research is needed. Lastly, this isn’t a magic bullet. Like most stats, it’s simply one more tool to help evaluate hitters, part of a patchwork.

It works well when combined with average exit velocity and possibly even max exit velocity (though Chamberlain didn’t specify max EV- that’s my own estimation). If a hitter hits the ball at the same angles frequently and hits it hard- at a high EV- they’re almost certainly very good. I should note that I’m paraphrasing Chamberlain’s work here and I strongly recommend reading the full article where he lays everything out.

An interesting Cardinals-related nugget in all of this is that Matt Carpenter has the seventh best/lowest StDev(LA)- 23.0- in the Statcast era (min. 1,600 batted ball events since 2015), per Chamberlain.

The second evaluation tool comes from Jeff Zimmerman, whose recent work sits neatly alongside Ben Clemens’ impressive A Sweet Spot by Any Other Definition piece from late February. Both Zimmerman’s recent articles (the introduction and the follow-up with analysis of specific players) and Ben’s article gets at the fact that, while hard contact is great, not all contact is created the same. Zimmerman’s work includes a metric named AHHD (Average Hard Hit Difference). The definition:

Average Hard Hit Difference: The difference between the HHLA and the angle for the sub-98 mph hits. From yesterday’s research, hitters start to see a production decline at a 0 AHHD and it accelerates around -4.4 AHHD. Basically, the batter is trying to get too much loft and his batted balls are going for weak flyouts.

HHLA is hard hit launch angle- a hitter’s average launch angle on batted balls with an exit velocity of 98 or more mph. As Zimmerman notes in the initial piece, max exit velocity is still a major factor. A higher max exit velocity will mean more production when evaluating two players with the same AHHD. He also identifies several categories. They’re broken down by max EV buckets (under 109, between 109 and 113, and 113+) and/or AHHD higher than -4.4.

There are a lot of implications for AHHD. When reviewed on a rolling basis in conjunction with average launch angle, max EV, and average EV, you can decipher whether or not a hitter has changed, either for better or worse. That’s precisely what Zimmerman did for his second article.

Here’s how the Cardinals fared in these metrics last season, along with their change from 2018. I’m including players who have left (José Martinez, Jedd Gyorko, Marcell Ozuna, Yairo Munoz) and newcomers (Austin Dean). I had to recreate the data from scratch to determine their change from 2018. You’ll see that my data is slightly different from Chamberlain’s and Zimmerman’s. I can’t tell you how or why my results came out slightly different. Just know that you can find the original info in their articles.

2019 Cardinals AHHD and StDevLA

Year Player StdDev LA Max EV AHHD StDevLA +/- AHHD +/-
Year Player StdDev LA Max EV AHHD StDevLA +/- AHHD +/-
2019 Matt Carpenter 25.14 108.9 7.85 2.54 5.64
2019 Dexter Fowler 25.66 111.1 5.51 -2.89 4.91
2019 Jose Martinez 23.79 110.8 4.48 -0.07 2.62
2019 Harrison Bader 29.60 111.2 2.75 2.08 1.70
2019 Yadier Molina 24.95 106.2 2.36 0.77 -0.16
2019 Paul Goldschmidt 25.15 111.5 2.09 -1.08 1.55
2019 Matt Wieters 25.83 106.4 1.71 -2.05 0.54
2019 Marcell Ozuna 26.97 115.3 1.24 -0.08 2.40
2019 Austin Dean 26.01 113.1 -0.56 -2.46 4.27
2019 Kolten Wong 29.32 107.7 -0.99 -1.09 -2.51
2019 Yairo Munoz 25.98 107.9 -1.36 0.60 -11.14
2019 Paul DeJong 26.72 111.7 -2.52 0.64 -2.90

Some observations...

  • If we limit our scope to all players with 250 batted ball events, José Martinez ranked in the top 20 in StDev(LA) in both 2018 and 2019. In other words, it verifies what we’ve always known- that Cafecito is a well-rounded hitter. In addition to lots of plate coverage, you can now add bat control to his superlatives. Of course, the quandary is that his average launch angle in 2019 was 6.8, which sapped him of production.
  • There’s an entire article to be written about Matt Carpenter, whose StDev(LA) went in the wrong direction. Considering Chamberlain’s consideration that it may be a sign of either age-related decline or injuries, and that Carpenter is an older player who also dealt with injuries throughout the season, there’s a lot of fun to be had trying to untangle which of those two items caused his 2019 decline.
  • Dexter Fowler’s drastic improvements from a dreadful 2018 really show up in the +/- categories. He shaved almost three degrees off of his StDev(LA) and increased his hard hit launch angle. It’s no wonder that his full season results were significantly better.
  • Paul Goldschmidt improved in quite a few categories but was victimized by a dip (not shown in the table) in max EV and average EV. His approach improved a little but his ability to hit the ball very hard slipped, which is something to watch whenever baseball resumes.
  • Tyler O’Neill’s hard hit launch angle collapsed in 2019, from 25.1 in 2018 down to 15.5. Like Carpenter, he also had multiple nagging injuries but it’s also worth wondering if he didn’t modify his approach.
  • Harrison Bader improved his launch angle and AHHD, but his StDev(LA) took a hit. There’s a tendency to think of his 2019 as being a result of batted ball luck, but considering StDev(LA)’s relationship to BABIP, perhaps he just had less consistent bat control last year.
  • Paul DeJong’s 2018 and 2019 were reasonably similar by average launch angle, max exit velocity, StDev(LA), and even launch angle under 98 mph EV. Where it all went wonky- and the reason his AHHD dipped closer to the dreaded -4.4 figure- is that his hard hit launch angle dropped almost three degrees.

I’ll have more analysis using these tools in the coming weeks, and they’ll be part of the thought process in general when looking at hitters once baseball returns.. Carpenter alone seems like a riddle ripe for analysis.