Reactions were mixed when the Yankees traded Shane Greene and landed Didi Gregorius in a three-way deal with the Tigers and Diamondbacks. After the trade, word got out that Gregorius, like Chase Headley, intrigued Brian Cashman becasuse of his ability to consistently hit the ball hard. Cashman had originally decided to pull the trigger on Headley because his "hit velo" had improved.
Brian Cashman said Headley’s been a lot better since getting an epidural for herniated disc. Said his "hit velo" has jumped. #Yankees— Jorge Castillo (@jorgeccastillo) July 22, 2014
Gregorius, like Headley, is a buy-low player to the naked eye, but his quality of contact suggests that he should be a much better hitter. Inside Edge, a video-based scouting service, had Sir Didi's "hard hit rate" at the same level as Mike Trout and Justin Upton, according to ESPN New York's Mark Simon. Fangraphs' Jeff Zimmerman used Inside Edge's hard hit rate and players' speed to create a stat called xBABIP, short for Expected Batting Average on Balls in Play. Gregorius's 2014 xBABIP was .330, 73 points above his actual .257 BABIP.
The short version is that Didi Gregorius is a better hitter than his current numbers indicate. But one major obstacle for Gregorius is the fact that he is a fly ball hitter for no good reason. In 2014, his fly ball rate of 42.9% was 37th among hitters with at least 250 plate appearances, which puts him slightly below the 90th percentile. As his batted ball splits show, he is hurting himself by hitting that many fly balls, courtesy of Fangraphs:
|Batted Ball Type||BA||SLG%||wOBA||wRC+|
It is worth noting that at least 99.9% of hitters' line drive splits are better than their fly ball splits. But for hitters with a high home run to fly ball ratio (HR/FB), the tradeoff of a fly ball-oriented swing is worth it since home runs are guaranteed runs, whereas other base hits require runners to be driven in. Gregorius' 2014 HR/FB ratio was well below average, at just 6.4%. If he did not make any adjustments, that number would probably creep up at Yankee Stadium. But it is hard to imagine the traditionally light-hitting shortstop turning into Jason Giambi as a Yankee.
For Didi to reach his ceiling, there are two logical courses of action. First, he can hit more line drives. Second, he can bulk up and hope the added strength improves his HR/FB ratio. The latter would make him too big to play shortstop, so the line drive route looks a lot more feasible. To be clear, I don't know
much anything about hitting mechanics, but to my untrained eye, it looks like Gregorius uses a long and heavy bat, similar to that of Alfonso Soriano (another high fly ball, low line drive hitter):
Maybe something about a heavier bat causes the bat head to lag and results in hitters getting under the ball more than they should. Notice how much Gregorius is choking up on the bat in the GIF above. Perhaps a lighter bat would help Sir Didi hit more line drives. If not, the Yankees clearly believe new hitting coaches Jeff Pentland and Alan Cockrell can fix the team's offensive woes. Either way, there is no reason not to err on the side of cautious optimism when it comes to Derek Jeter's successor in 2015.