It is no secret that Chase Headley's 2015 campaign has not gone as planned. He is putting up a meager (.235/.289/.379) batting line, while faltering in the field as well. While he is a traditionally slow starter (103 career wRC+ in the first half, 126 in the second half), Headley's struggles are pretty rare considering his unique tendencies as a hitter.
What makes Headley's struggles so unique, strangely enough, is that he is doing two things well. First, he is continuing to hit plenty of line drives as a Yankee. Headley owns a 21.2% career line drive rate, but that number has jumped over 27% during his short tenure in pinstripes. He also is an extreme pull hitter, which is a good thing at Yankee Stadium, as a handful of Hall of Famers can confirm. But put those two traits together, and you begin to run into a bit of trouble.
Last season, Headley and Chris Davis were the only qualified hitters to finish in the top 20 in line drive percentage and pull percentage. Davis was coming off a huge BABIP shock and came crashing back down to earth with a 94 wRC+, just a season after finishing third in the AL MVP voting. Hitting lots of line drives usually bodes well for a hitter's BABIP, but drawing a shift doesn't. As a Yankee, Headley's flyball percentage is below league average, the opposite of what a pull hitter should be doing.
In the case of Chase Headley, either his line drives or his pull hitting have to go. Of course, there are hitters who hit fly balls and pull the ball, but don't play well (see: Stephen Drew). So should Headley go for more fly balls or try using all fields? Because of his contact quality stats, it's hard to tell.
Baseball Info Solutions, a company that tracks every pitch of every game, says Headley's "hard hit percentage" was over 35% for the last three seasons, which is above league average. This season, that number is back down to 30.8%, but that is with Headley's plate discipline taking a bit of a hit this season. His walk rate is half of what it was during the second half of 2014. According to Baseball Savant, balls leave Chase's bat at an average of 85 mph, not exactly the fastest. The general consensus is that exit velocity correlates very well with bat speed. Unfortunately, exit velo data before 2015 is not available to the public.
For Headley, the question is just how hard he hits the ball. If his diminished hard hit rate is related to him swinging at more bad pitches this year, he should shore up his plate discipline and try to hit more fly balls. If he actually just doesn't have that much bat speed, he should look to spread his line drives out across the diamond. The Yankees traded for Headley after seeing his exit velocity increase after a midseason back procedure, so they have a better idea of what he should be doing.
In conclusion, Chase Headley is a very good hitter. Having a line drive rate north of 27% is impossible for players who cannot consistently square up the ball. But by lining a bunch of balls to the same area every time, he is wasting that ability. He might want to hurry up and turn things around. Eric Jagielo is not exactly having too much trouble at Double-A Trenton, just saying.
Unless stated otherwise, data is from FanGraphs.