Yankees: The evolution of Didi Gregorius

Didi Gregorius has improved every season since he was traded to the Yankees, transforming himself from a glove-only shortstop to the all-around superstar he has been thus far in 2018.

First, it was he couldn’t hit at all. Then, it was he couldn’t hit against lefties, followed by he could never hit for power. All along the way, Didi has continued to prove his doubters wrong and has successfully entrenched himself as the starting shortstop for the New York Yankees, something that once seemed unthinkable when he was tabbed as Derek Jeter’s replacement.

After coming close to earning his first All-Star bid last year, Gregorius looks like he will leave no doubt this year. To date, he’s been the best player in baseball by a solid margin. He’s second in batting average and leading the league in SLG, OPS, HRs, and RBIs while also playing gold-glove defense.

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What’s the cause for his gaudy offensive improvement? Sir Didi has corrected the one remaining flaw that was left in his game: his plate discipline. He’s noted his change in approach to reporters, saying to Newsday:

"“[I’m] sticking to a game plan. Just see how the guy pitches you and try to stick to that. If he’s trying to pitch around you, just take a walk, which everybody knows I don’t walk that much. So I’m learning to try to lay off those pitches and try to get on base for the next guy.”"

The results speak for themselves. Gregorius already has 17 walks on the season, he’s tied for 13^th in the MLB after finishing with 25 and 18 BBs in 2017 and 2016 respectively.

Looking even deeper into the advanced statistics, his overall swing percentage (Swing%), swing percentage on pitches outside the strike zone (O-Swing%), and swing percentage on pitches inside the zone (Z-Swing%) have all substantially decreased from his previous two breakout seasons.

When you have great bat-to-ball skills like Didi, it can actually play against you if you tend to be a free-swinger. This is due to the generally weak contact-induced when hitting pitches out of the strike zone and also with tough strikes. By being more selective at the plate, Didi has laid off more of the tough pitches and has been taking hacks at mainly at the ones he knows he can drive.

This is likely one of the main reasons why his power numbers and overall offensive statistics are way up to start 2018. The other reason? Gregorius has continued to increase his fly ball rate (FB%), which may be even more important given the dimensions of Yankee Stadium.

It’s no secret that all 77 of his career HRs have been pulled to right field. Didi himself doesn’t identify as a homerun hitter, and it’s not like he’s a hulking slugger like Aaron Judge or Giancarlo Stanton. His batted ball profile is perfect for Yankee Stadium, and while he isn’t a behemoth, he’s more than strong enough to hit liners over the short porch.

Since he’s elevated his pull rate, he’s also staying away from the deepest part of any ballpark (center field), therefore maximizing the chances the ball leaves the yard. Not only is he hitting the ball in the air more and pulling it, but his launch angles have been near optimal. Typically, launch angles between 15 and 25 degrees are the most desired, while the average launch angle for players in 2017 was 11.83 degrees.

Gregorius currently has the sixth highest average launch angle in the MLB at 22.74 degrees, while the others ahead of him are slightly inflated due to more extreme ranges compared to Didi’s more consistent profile. Check out this image, courtesy of Baseball Savant:

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Look at how heavily concentrated his launch angles are between 15 and 25 degrees. This is a special start to a season, and while his numbers are not sustainable (currently on pace for 62 HRs and 186 RBIs), it seems clear that Didi has evolved into one of the best players in the game.