Corey Dickerson's struggles at the Trop

When Corey Dickerson was traded from the Rockies to the Rays in January he was be confronted with the same skepticism that follows all hitters departing Colorado. Could he maintain a high level of production after leaving the Rocky Mountain paradise that is Coors Field?

Through 134 games in his first taste of the American League, Dickerson has recorded a slash line of .243/.288/.460 with a wOBA of .313 and a wRC+ of 97. Not a total disaster by any means but certainly not quite what the Rays were hoping for when they acquired him. Changing leagues is a process however, and when that change also entails leaving the most hitter friendly park in baseball, growing pains are to be expected. New parks, new pitchers, heck, new rules!

What follows is an examination of how Dickerson’s production with the Rays has differed from his time with the Rockies.

First off, we see the most basic of changes…

Dickerson is no longer playing in the field everyday.

For the first time in his career Dickerson is seeing extensive playing time as a designated hitter. The simple act of not being involved in all aspects of the game does have a quantifiable effect. Mitchel Lichtman has shown that the "DH penalty" is about 14 points of wOBA. For Dickerson it has been even more pronounced. In 232 plate appearances as an outfielder he has posted a .344 wOBA but in 243 plate appearances as a DH he has seen that number fall to .298, a 46 point difference. It's a small sample, but the results thus far have not been encouraging.

As Joshua Morgan from D-Rays Bay points out, playing left field next to Kevin Kiermaier has helped Dickerson quite a bit as a defender. The metrics have seen him post a positive +1 DRS and a fantastic 6.8 UZR. Of course defensive metrics are hard to trust in such small samples, and the team may have proprietary data suggesting his defense is not so positive, but on the surface it appears that the Rays should keep Dickerson in left field as much as possible in order to maximize his offensive potential.

No matter what his position, one fundamental aspect of his game has changed drastically…

Dickerson's fly ball rate has skyrocketed.

For the three years that he played in Coors Field, Dickerson’s batted ball profile remained relatively consistent. It hasn’t been until his first year in Tampa Bay that it has seen a dramatic shift. Dickerson’s fly ball rate has increased 12.3 percentage points from 2015 to 2016. That wouldn’t be all bad if the fly balls were coming out of his ground ball rate, but instead he’s exchanging line drives for fly balls, and that’s not ideal.

An increased fly ball rate isn’t the end of the world for someone with Dickerson’s power since he’ll be able to turn many of those fly balls into extra base hits and home runs, but line drives are the batted ball type that most often leads to a hit, thus converting so many of those batted balls from line drives to fly balls will assuredly decrease the frequency with which Dickerson finds himself on base.

The increase in fly balls is a partial explanation as to why…

Dickerson’s batting average on balls in play (BABIP) has taken a huge hit.

In 2014 and 2015 while playing his home games in Coors Field, Dickerson carried robust (and largely unsustainable) BABIP marks of .356 and .367. Unfortunately for him the chickens have come home to roost as he has seen his 2016 BABIP fall to .284. While his current mark is not alarmingly below the league average BABIP of .300, a .083 drop is significant.

Take a look at how the Rockies and Rays have ranked respectively in home BABIP for the last three years. It’s clear that the environment in Colorado is exceedingly conducive to carrying a high BABIP.

A drop off in BABIP of the magnitude experienced by Dickerson should not have taken anyone by surprise. The move from Coors Field to Tropicana Field along with the increase in fly balls has had a serious impact on how many of Dickerson’s balls in play are falling for hits. It’s worth wondering if the change in home parks is also part of the reason that…

Dickerson has been decidedly better on the road in 2016.

In the exact same number of games played and only 16 more plate appearances he has been fantastic on the road and just awful at Tropicana Field.

Without being able to ask Dickerson directly if his approach at the plate is altered when playing at home, we can only speculate on any differences. Conscious change or not, he is definitely going up the middle much more often on the road (38.4 percent) than at home (27 percent). This is perhaps due to the unusual center field dimensions at play in Tropicana Field. As you can see from this spray chart of all the balls Dickerson has put in to play this year, deep center field in Tampa Bay is an area that remains relatively unexplored.

(Tampa Bay’s dimensions are depicted on the left slider.)

Add to this that his home run power has been to all fields on the road and exclusively to the pull side at home and it’s not unreasonable to wonder if Dickerson is letting the ballpark he plays in dictate his approach at the plate.

The approach is but one facet of an at bat though. Perhaps the most important difference in his first year away from Coors Field is that…

Dickerson is seeing fewer fastballs than ever.

In his first three years in the Major Leagues, pitchers were throwing Dickerson fastballs about 66 percent of the time. Now in his first year in the American League that number has dropped to 58 percent. That difference is now that he is seeing an increase in off-speed pitches by a little more than two percent and in breaking pitches by almost five percent.

It has been proven that pitch movement is hindered a bit in the high altitude of Coors Field. This is true for all pitches but especially for breaking balls. So when we look at the FanGraphs’ Pitch Type Values for Dickerson this year compared to his previous years it’s not a complete shock that he seems to have struggled more than ever against pitches that rely on movement for effectiveness.

It’s not unreasonable to suggest that Dickerson’s newfound struggles against the curveball, changeup, and split finger are the result of being exposed to more movement on these pitches than he had previously. On curveballs specifically, according to Statcast he faced an average spin rate of 2231 rpm in 2015 and has seen that increase to an average of 2530 rpm in 2016. More spin on a curveball means more drop. Meanwhile, Dickerson remains effective against the two pitches that are least affected by the altitude of Coors Field, the fastball and slider.

Admittedly this is a theory that does not take into account the quality of pitchers and their arsenals. So while positing that the move out of Coors has exposed Dickerson to more consistently high level breaking pitches is just a hypothesis, there does appear to be some validity to the claim. Dickerson’s ability to adjust to how pitchers are attacking him now, post-Coors field, will be the key to his value going forward.

***

The Rays won the Corey Dickerson trade the moment they made it by acquiring a 27-year old outfielder with a tremendous ceiling and four years of team control for Jake McGee, an excellent 30-year old relief pitcher, but a fairly replaceable relief pitcher nonetheless. The fact that McGee has been terrible for the Rockies is of no consequence because regardless of what has unfolded on the field, the Rays’ process was sound in making the deal.

While the adjustment to a new league and a new park haven’t gone as smoothly as Dickerson or Tampa Bay would have hoped, all is not lost. Even if his production stays as it is currently, the Rays still have themselves a useful strong-side platoon outfielder. And if he can recapture just a little bit of his lost line drive rate and carry his all-fields approach from the road into home games at Tropicana Field, Dickerson will find himself able to shake the stigma of having begun his career at Coors Field.