Which Yankees hitters changed the most in 2018?

Baseball players are dynamic. Not all in the way that, say, Javier Baez is dynamic, but in that their performance can change dramatically. Now, many year-to-year changes in performance can be chalked up to variance, or to a guy just having an off season. Most of the time, when a player sees a fluctuation in performance, it’s not actually because he suddenly became a completely different athlete.

Sometimes, though, players can change fundamentally, or at least perform in a way that’s clearly different from the past. In prior years, I’ve analyzed the Yankees that changed the most. Last year, I wrote about how Aaron Judge changed in terms of his contact ability, and how Didi Gregorius became a better power hitter.

Those were obvious changes. This year’s Yankees lack such clear differences. Some players saw their performance change, to be sure, but just because, for example, Gary Sanchez had a worse season in 2018 doesn’t mean he was a fundamentally different player in than in 2017.

It’s harder to see players that underwent real changes in 2018, but there still must be something there. Let’s take a look, starting with:

Gleyber Torres

Torres wasn’t even with the Yankees prior to 2018, but stay with me. He was a revelation early in the season, in large part due to his power hitting. He burst onto the scene and blasted past expectations because he was able to hit the ball with a level of authority most scouts and analysts could not have predicted.

Before the season, FanGraphs’ Steamer projections pegged Torres for seven home runs in about a half season’s worth of plate appearances, along with a paltry .381 slugging. ZiPS projections were rosier, but still only forecast him for a .441 slugging percentage. The projections were lukewarm on Torres’ power because he didn’t hit for much of it in the minors.

Torres hit one home run in 14 games in the minors in 2018. He hit seven in 55 games in 2017. He hit 24 total in his minor league career, across 1602 plate appearances, and slugged .410. Minor league statistics are far from a be-all-end-all, but it’s obvious why the statistical projections systems didn’t see Torres as a power hitter.

Moreover, scouts didn't expect Torres to hit for power right away Entering the year, FanGraphs gave Torres’ game power a grade of 40 out of 80 on the scouting scale, which is below average. MLB.com wrote that Torres could hit 20+ home runs at his peak, but not necessarily at the outset.

Before injuring himself in early July, Torres hit 15 homers in his first 63 major league games. He slugged an eye-popping .555. He was legitimately one the league’s best power-hitting middle infielders immediately upon entering the Yankees’ lineup.

Of course, Torres did get hurt, and the injury did seem to hamper him. He slumped in the summer, which brought his overall numbers down. Torres still hit 24 bombs and slugged .480 in 123 games in his rookie year.

Part of this is surely due to the differences in composition between the ball in the minors and majors. Homers overall were down a bit in 2018, but home run rates were still high, and higher than in the minors. A rookie like Torres stood to benefit from that.

Even so, Torres hit for a level of power that was entirely unforeseen. His reputation was as a player with a great hit tool and the potential to some day hit for some power. This year, he quickly changed into a player that could hit for great power right now.

Giancarlo Stanton

This feels like a bit of a stretch. Like I said before, the Yankees lacked players that clearly fundamentally changed this year. Stanton probably didn’t fundamentally change as a player this year, but he did, however, see his process change in his first year as a Yankee, and not entirely for the better.

When Stanton scuffled a bit early in the year, it seemed like he was pressing. The narratives that he is overpaid or not cut out for New York are silly and overblown, but it would have been understandable if Stanton was trying to do a little too much as he transitioned to pinstripes.

What Stanton was trying to do this year is unknowable, but his numbers aren’t. Per FanGraphs, Stanton’s chase rate spiked this year, from 27% in 2017 to 32% in 2018. Swinging at bad pitches more often leads to more whiffs, and more whiffs means more strikeouts. His strikeout rate flew up from 23% last year to nearly 30% this year.

It’s not unreasonable to think that Stanton could have pressed a little and expanded the zone too much this year. Heck, he certainly appeared to do so during the postseason. Elsewhere, Stanton's batted ball profile was also changed. He used the whole field more than ever, posting a career-low pull rate, and a career-high opposite field rate. Given Stanton’s career 267 wRC+ on pulled balls, that isn’t exactly a positive development.

That being said, even as Stanton’s fundamentals changed this year, I hesitate to say he really changed. Unlike Torres’ newfound power, I don’t expect Stanton’s changes to stick entirely. In fact, while Stanton did change this year compared to last, he has reached these levels of chasing and whiffing before. Our own Kento Mizuno outlined last month how some of Stanton's worse play this year simply looked like normal variations in his own established performance.

So Stanton did change this year, but with any luck, it won’t be a change that lasts. He still maintained his prodigious ability to terrorize baseballs, and as long as Stanton has that, he’ll be an incredibly valuable member of the team.