Thursday, March 4, 2021

Inside the Dodgers: Explaining the paradox of Corey Seager’s 2020 success


Editor’s note: This is the Wednesday, March 3 edition of the Inside the Dodgers newsletter from reporter J.P. Hoornstra. To receive the newsletter in your inbox, sign up here.


One curiosity of the 2020 season stuck to my brain and didn’t let go throughout the off-season. Prior to the pandemic, Corey Seager famously watched video of his plate appearances during games. MLB banned the practice last year, among many restrictions designed to reduce the spread of the novel coronavirus. In theory, that might have sent Seager’s numbers plummeting. Instead he had the best offensive season of his career (in 70 games).

Writing about this paradox for the Wall Street Journal, Jared Diamond noted how other stars, including Javier Baez and J.D. Martinez, said their inability to watch video mid-game caused them to slump at the plate. Seager couldn’t explain his own success. “I’m definitely eager for it to get back to normal,” he said. “There are certain things that you feel that you think are in the right spot and they’re not. It’s been a year of relying on feels, and that could be good and bad.”

Operating on the assumption that there has to be an explanation for Seager’s success, I decided to dig into his numbers. I found what looks like a partial answer.

If we’re interested in the effect of watching video between plate appearances, it makes sense to start by comparing Seager’s results from his first plate appearance to his second to his third. Baseball Reference has the counting stats for a batter’s 1st time facing a starter vs. 2nd vs. 3rd. We can see that, in terms of OPS, which is a good proxy for run production, Seager was noticeably better last year in his 1st and 2nd plate appearances against opposing starters compared to years past. His 3rd plate appearances against opposing starters in 2020 were slightly poorer by OPS compared to 2019, and to his career on the whole.

You can fit a theory to this data. Seager’s access to videos before and after games were the same in 2019 and 2020. His performance in his first plate appearance of every 2020 game shouldn’t have been affected by in-game video access ― only whatever adjustments he made before the 2020 season and between games. Knowing that his first-PA OPS jumped 200 points (from .938 to 1.139) tells us that Seager made significant strides that had nothing to do with his in-game habits. But how do we explain Seager’s second-PA success, a jump in OPS of almost 300 points (.841 to 1.132)? Hitters don’t always see the same pitches (by location, type, velocity, etc.) in their second plate appearance that they saw in their first ― especially hitters who tend to swing early in the count, like Seager. Maybe seeing a pitcher for the second time in the game, for Seager, was not much different from seeing him the first time. By the third plate appearance, however, pitchers ostensibly figured out something about Seager’s approach and adjusted to their advantage. Seager’s inability to access video in-game seemed to turn the “third time through the order penalty” on its head.

There’s a danger in fitting a theory to a sample size that small. Seager only faced an opposing starter three times in a game 34 times last season. We need more than 34 data points to forge any conclusions about what was actually happening with confidence. We’re also glossing over an important effect of in-game video: pitch recognition. Better pitch recognition results in a better OPS. But we still don’t know how a lack of in-game video affected Seager’s ability to recognize and react to specific pitches from one plate appearance to the next.

MLB.com’s Statcast data allows us to dig in to some of these specifics. It has a tool called “swing/chase” that displays hitters’ tendencies to swing or lay off pitches thrown to one of four different zones: the heart (middle), shadow (pitches on the border of the strike zone that are called balls half the time), chase (just outside the shadow) and waste (nowhere near the strike zone). Here is Corey Seager’s “swing/chase” chart.

That chart tells us a lot, but not for our purposes. It’s missing a breakdown of what happens to Seager’s swing/take tendencies from one plate appearance to the next. But we can figure this out, albeit crudely, through the Statcast search engine.

Sample size is our biggest obstacle when slicing this data by pitch type. It’s too easy for one pitch in one at-bat to skew the data. Here’s a great example: Seager saw 21 changeups in his third time through the batting order during the 2020 regular season. One of those (against the Rockies’ Carlos Estevez on Sept. 17) resulted in an extra-base hit, a double. Yet Statcast credits him with an expected slugging percentage of .857. More than an indictment of how Statcast calculates expected slugging percentage, I think this demonstrates the limits of using 21 data points to draw sweeping conclusions about a batter’s season.

So, let’s ignore pitch type and focus on location. When we use the same four location classifications (heart, shadow, chase, waste) that we have for the “swing/chase” analysis, a clear picture emerges of where Seager is looking to make his money. Sample size is still somewhat of an issue, but less so when categorizing every pitch Seager saw into four zones as opposed to, say, 10 different pitch types. For this analysis, then, we’re looking at two things: what Seager did against pitches thrown to one of four locations, and how that changed from one plate appearance to the next.

What jumps out first is how dangerous Seager was on pitches thrown down the heart of the plate in his first plate appearance. His average exit velocity when putting these pitches in play was 100.2 mph. Compared to past seasons, Seager put more of these pitches in play, and he was rewarded with an expected slugging percentage of .990. That ranked 25th out of 330 players who batted at least 10 times in 2020.

That’s impressive, but consider what Seager did against “shadow” pitches ― pitches that are called strikes half the time and balls the other half. Seager wasn’t as aggressive against these pitches his first time at-bat, but when he swung at them he was nearly as dangerous. His expected slugging percentage of .894 was second in MLB. That exceptional degree of selectivity wasn’t present for Seager in seasons past. Was this just a small-sample quirk of a shortened 2020 season, or a repeatable skill that can carry over to 2021? This is an important question for Seager and the Dodgers.

Seager didn’t put any balls in play on “chase” pitches in his first plate appearance in a game last year, but his .600 expected on-base percentage indicates that he laid off these pitches regularly. Now we have a more complete picture of Seager’s impeccable first-plate-appearance success. (Waste pitches are relatively uncommon, and so rarely put in play, that we can safely ignore them for purposes of this analysis.)

Looking only at his second plate appearances in 2020, here’s what Seager did against pitches in the heart and shadow of the strike zone. Compared to his career numbers, Seager was exceptional in these situations. He also continued to lay off pitches in the “chase” region, only striking out once on a chase pitch in his second plate appearance of a game in 2020.

So far, all of these numbers support the surface-level stats I cited at the beginning of this newsletter. So, what happened his third time up to the plate? Seager stopped crushing pitches located in the heart of the strike zone. Counterintuitively, he fared better against pitches in the “shadow” than the heart. He wasn’t chasing an inordinate number of pitches in the “chase” zone, only striking out twice. But for some reason Seager wasn’t crushing the pitches that should be easiest to crush in his third plate appearance, and that had a noticeable effect on his counting stats.

There’s no shortage of hypothetical explanations for why this happened. Maybe Seager was regularly looking for a pitch in one location his third time up, and getting another. Maybe by that point in the game ― probably the fifth inning or later ― Seager wanted to take the first pitch he saw to establish some measure of rhythm, and as a result he wasn’t as confident swinging even when those pitcheswere right down the middle of the plate. If that’s the case, maybe watching video prior to his third plate appearance had been providing Seager that confidence in years past. Again, it would be nice to have more self-reporting insight from Seager. When we asked him last October, he either wasn’t aware of what was happening ― or comfortable enough in his self-awareness to provide an explanation to the media.

At least there’s enough publicly available data to suggest where Seager can look to make an improvement on his 2020 season. More than that, last season shows that Seager has plenty he can build on. He wasn’t “getting lucky” late in games despite not being able to access video of his at-bats. He was somehow better equipped as a hitter ― physically and/or mentally ― going into each game, and that made a world of difference.

-J.P.


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