Didi Gregorius' bat continues to defy expectations. Convinced that he was a glove-first shortstop, I was already surprised when he was a league-average hitter in 2016. Needless to say, I was shocked to see him hit 25 homers and post a 107 wRC+ en route to a 3.9 WAR season last year. However, what was truly notable about his 2017 season was not what he did, but how he did it.
As a hitter, good plate discipline is the cornerstone of a sound hitting approach. By plate discipline, I mean having the ability to a) recognize hittable and unhittable pitches and b) swing selectively at hittable pitches. But Didi didn't exhibit any of those qualities in 2017.
Last year, Didi posted the 6th-highest O-Swing% (40.8) and 3rd- highest Swing% (58.2) in all of MLB. Meanwhile, his walk rate of 4.4% was the 9th-lowest figure. For all intents and purposes, Didi was an unabashed hacker in 2017.
What does this mean for Didi's future success? Normally, I'd say that hacking away isn't really a sustainable long-term strategy. Swinging at, and making contact with, pitches out of the strike zone usually leads to weak batted balls that go for outs. Therefore, it's generally a better idea to not swing so much and make the pitcher throw strikes. However, Didi presents an exception to this rule. Didi has become a better hitter by being more aggressive, and maybe he should stay that way to keep on keepin' on.
Looking at Didi's career trajectory, an interesting correlation comes up. Disregarding his 2012, in which he only played 8 games, Didi's wRC+ has improved as his Swing% has progressively increased:
Not only that, but his steadily increasing O-Swing% hasn't really affected his contact quality:
So it seems that Didi's trigger-happy ways have aided his offensive improvements, and the side effects of his aggressiveness - namely, swinging at balls - haven't really been felt in terms of his contact quality. What gives?
A simple yet convincing theory was given by PSA commenter thedraftking, in the comments to my previous Didi article:
Tl;dr: While Didi is still swinging at a lot of balls, he is also swinging (and making contact with) a lot of strikes, which helps him maintain his contact quality and get more hits.
Is this true? Time for another graph:
Kudos, thedraftking, your theory holds up. What this graph tells us is that a) Didi has always had above-average bat-to-ball skills, and b) by swinging at more strikes, Didi has been able to utilize those skills to increase his offensive production. In this regard, Didi hasn't succeeded despite his poor plate discipline; rather, he's succeeded because of it.
To wrap things up, we've seen that Didi's aggressive tendencies at the plate help him more than it hinders him, because it allows his contact skills to shine, offsetting the weak contact he generates by hitting bad balls. In this way, Didi isn't just a good hitter per se, but an important piece in the Yankees' lineup.
The Yankees, as currently constructed, feature a ton of hitters with patience and power. However, due to their patient ways, they are prone to falling into many two-strike counts, which is a precarious situation to be in against good pitchers and/or bad umpires. It's situations like those where Didi could shine most, because his aggressiveness and contact skills allow him to force the issue rather than waiting for the opposing pitcher to slip up and hang a fat one. For his sake, and their own sake, the Yankees should let Didi keep swinging away.
All statistics and graphs courtesy of FanGraphs.