Which Yankees hitters changed their games the most in 2016?

Last week, we looked at Yankees pitchers that underwent pretty fundamental changes to their games. Most notably, CC Sabathia and Masahiro Tanaka altered their repertoires, seemingly in an effort to hide the ineffectiveness of their four seam fastballs. Now, let's take a look at which Yankee hitters changed their games the most 2016.

Finding a difference in a hitter's game can be a little harder than finding one with a pitcher. Changes that pitchers undergo are often obvious: a large drop or spike in velocity or a brand new pitch is tough to miss. With hitters, changes in approach or strategy can be more subtle.

Yet that doesn't mean they don't exist. In particular, the Yankees up-the-middle combination seemed to undergo some changes, starting with:

Didi Gregorius

2016 was largely a successful year for Gregorius. He continued to cement himself as a quality shortstop, setting a career high with 20 home runs and providing good defense at a premium position.

It was Gregorius' progress at the plate that was most significant. Gregorius entered 2016 with a paltry career line of .253/.316/.368 and an 86 wRC+. He bumped that up to .276/.304/.447 and a 98 wRC+ in 2016. His improved performance was underscored by a different approach at the plate.

Gregorius was never a patient hitter, as he began 2016 with a 50.1% swing rate in his career (figures courtesy of FanGraphs). He actually doubled down on that this season, ramping up his aggressiveness to extremely high levels, as his 55.4% swing rate ranked 7th in MLB. Gregorius essentially staked his claim as one of the most aggressive batters in the game.

Yet his contact skills didn’t take a hit even as he was swinging freer. His 90.6% zone contact rate and 71.7% out of zone contact rate were both career highs. His 82.9% overall contact was also a career high, despite the fact that he was swinging at more pitches than ever.

This is made even more remarkable by the fact that Gregorius added power in 2016. His .447 slugging percentage and .171 ISO both were career highs. His fly ball rate increased from 34.3% in 2015 to 40.1% in 2016, and his HR/FB rate rose to 10.4% in 2016, up from 6.0% in 2015.

This is a very strange combination. Typically, increased aggressiveness can lead to less contact, and an uptick in power is almost always associated with a decrease in contact. It remains to be seen if he can sustain this, but somehow, Gregorius managed to buck both the trends, and the result was his best season as a professional.

Starlin Castro

Starlin Castro didn't quite match the success of his double play partner in 2016. He closed the year on a hot streak, but it wasn't enough to pull up his season line: .270/.300/.433, a 94 wRC+, and 1.6 fWAR.

Even so, it seemed like Castro was genuinely making efforts to change his game and become a better player. In recent years, Castro had developed a reputation as an aggressive hitter who rarely used the opposite field. He pulled the ball over 40% of the time in 2014 and 2015, and rarely went the opposite way.

At the beginning of his first season in pinstripes, Castro made real changes to his approach to try and become a more balanced hitter. Jeff Sullivan of FanGraphs astutely noted in article this April that Castro noticeably was staying more closed at the plate. In that piece, Sullivan pointed to this photo of Castro’s swing in 2015:

and compared it instances like this in April of this year:

Notice how Castro was striding toward left field in 2015, but was striding toward the pitcher this April, seemingly in an effort to stay closed and use all fields. It appears Castro stuck with that change throughout the year. This is a photo of Castro from this past September in the Bronx:

Here’s another from August:

Castro clearly stayed more closed this year, rather than flying open like he did as a Cub. This seemed to have something of the desired effect, as Castro really did start to use all fields more: his opposite field rate rose from 20.6% to 25.2%, and his pull rate ticked down slightly from 40.8% to 40.0%.

So Castro did succeed in changing his approach in some way, but it didn't necessarily help his production. After posting a 140 wRC+ on pulled batted balls in 2015, he actually posted a 200 wRC+ on pulled balls this year. However, he ran a dismal 76 wRC+ on opposite field batted balls in 2016, down from 90 last year. The league average wRC+ on opposite field batted balls this year was 103.

Plus, Castro's approach appeared to deviate in other ways that may have hurt his productivity. While he managed to use all fields better, his tendency to be over-aggressive at the plate worsened. He set a career high in swing rate at 51.7%, while his contact rate fell to a career worst 78.2%. Basically an inverse of what Gregorius managed.

Castro made progress with his approach, but unfortunately, it didn’t come with the same results as Gregorius. Gregorius impressively turned himself into a different, more aggressive hitter this year without sacrificing the contact skills that helped him previously. Castro appeared to have a new strategy this year, but it didn’t necessarily work. Next year, we shall see if Gregorius can maintain his changes, while we’ll find out if Castro will scrap his new approach entirely.