Which Yankees hitters changed the most in 2017?

Last week, we delved into which Yankees pitchers changed the most in 2017. Not changed in the sense that their WAR increased the most, but changed in the sense that their underlying games showed up different last year. Masahiro Tanaka essentially started pitching backwards, while Aroldis Chapman became hittable for the first time in his career.

It stands to reason that the Yankees also saw plenty of change on the position player side. Let’s waste no time and dig right into which hitters changed their game the most, starting with the most obvious, biggest, most profoundly thunderous baseball boy:

Aaron Judge

Obviously, any player that submits an MVP-caliber year just one season removed from looking lost upon first reaching the bigs is likely to have undergone some major changes. Yet it’s an understatement to say that Judge was among the biggest changers on the Yankees. Judge, fundamentally, was one of the most different players in the league when compared to his previous self.

Again, we’re not simply saying that Judge improved his WAR total by essentially a full Mike Trout, and thus he was one of the most changed players in baseball (though that certainly was a nice development). Judge, when he first appeared in 2016, looked like an over-matched player, with loads of power but without the requisite hitting skills needed to succeed in the majors.

Judge did not change in terms of his raw power, obviously, but instead turned into a player that could actually make contact with high-level pitching. Judge’s swinging strike rate plummeted from an untenable 18% in 2016 to 13% in 2017, per FanGraphs. The only players to record as many plate appearances as Judge across the time frame and see a greater drop in swinging strike rate were Tommy Pham and Alex Bregman.

Conversely, Judges contact rate spiked from 60% to 68%, a still below-average rate, but again, the third-highest increase in the league, behind Pham and Bregman. In terms of simply putting the bat to the ball, Judge improved as much as almost anyone in baseball.

Perhaps just as importantly, Judge improved his plate discipline by a great margin. Part of Judge’s swinging strike rate in 2016 was due to his inability to lay off bad pitches. While his vulnerability on soft stuff low and away is still prevalent, overall Judge did a much better job laying off the junk in 2017. His out-of-zone swing rate was just 24%, significantly better than average. That represented a nine point drop from 2016, the largest such decrease in the entire league.

Swinging less at balls and making more contact when he did swing was more than enough to allow Judge to unlock his power potential, as the damage he does when bat meets ball is unprecedented. Going forward, Judge’s ability to continue to refine his approach, as he clearly did between 2016 and 2017, will be crucial, as opposing pitchers will surely try to mine whatever weaknesses he has for all their worth. The fact that Judge changed as much as any player in baseball bodes well for his ability to adjust to whatever his opponents throw at him.

Didi Gregorius

The shape of Gregorius’ production as a Yankee has always been changing. When he was first tasked with replacing Derek Jeter after being acquired for (literally) Shane Greene back in 2015, Gregorius was a light-hitting, slick-fielding kind of shortstop. He’s gradually evolved since then into a player that can contribute on both sounds of the ball and has established himself as a first-division starter at shortstop.

Much was made of his acension as a power hitter in 2016, when he smashed 20 home runs for the first time in his career. Yet there were reasons to be skeptical of his sudden proclivity for power, given there was little about his batted ball profile that had changed to suggest that he was suddenly someone that could reliably fit in the middle of a quality lineup.

However, Gregorius set a club-record for homers hit by a shortstop with 25 in 2017. Gregorius’ ability to provide power looked more real by the day in this past season, and unlike 2016, he brought some reasons to believe that he’d actually changed as a hitter.

After watching Gregorius set a career-high in homers in 2016, you’d have been forgiven for guessing that Gregorius had curtailed his groundball rate, and started pulling the ball in the air more in an effort to yank more balls into the right-field bleachers. None of that actually happened in 2016, but in 2017, Gregorius’ batted ball profile really did change as he set more career-highs.

Gregorius’ fly ball rate was a career-high 43.8% in 2017, and subsequently, his 36.2% groundball rate was a career-low. He pulled balls more than ever, over 40% of the time. Gregorius really did turn into a more pull-heavy, air-ball hitter (though curiously, despite a profile well-suited for Yankee Stadium’s short porch, he didn’t actually perform better at home).

It’s easy to see this development in Gregorius’ spray charts, courtesy of Baseball Savant:

Gregorius clearly put more balls in the air and to his pull side, which surely contributed to his increase in power. Now, Gregorius’ profile changed last year, but there are notable ways in which he didn’t change. He still doesn’t hit the ball hard, and his average home run distance (377 feet) ranked 317th out of 333 players with 150+ batted balls. While Gregorius did change as a hitter, if he doesn’t start hitting the ball harder, it’s easy to see him regressing from his current power output.

That being said, Gregorius provided more reason to believe in his boost in power in 2017 than in 2016 thanks to new batted profile. That, combined with his typically strong work in other areas of the game, is more than enough to make him one of the Yankees’ best and most dynamic players. Even if he doesn’t manage to strike the ball with more authority going forward, he’ll still in all likelihood be a major part of the Yankees’ success.