Nicholas Castellanos Crushes Fastballs, but That’s About It

Evidently, Nicholas Castellanos doesn’t love playing in Comerica Park.

“This park is a joke,” he told Chris McCosky of The Detroit News on July 21. “It’s to the point where how are we going to be compared to the rest of the people in the league in terms of power numbers, OPS, slugging and all that stuff when we got a yard out here that’s 420 feet straight across center field?”

As we approach the July 31 trade deadline, it appears likely that Castellanos won’t have to call Comerica home for much longer. The Tigers are 30-67, and as MLB.com’s Jon Morosi reported on Wednesday, they are “virtually certain” to trade him by the deadline. But a change of scenery might not be the solution to Castellanos’ problems. Playing the majority of his games in Detroit isn’t why the outfielder has taken a slight step back this season (130 wRC+ in 2018; 114 wRC+ in 2019).

First, let’s dispense with Castellanos’ claim. Here are Castellanos’ 2019 home and road splits:

Those are some pretty drastic splits, but it’s clear that Castellanos is not being hindered by the effects of Comerica Park. The wRC+ split ⁠— which, as we know, adjusts for park factors ⁠— tells the full story. While Castellanos has been a better hitter on the road than at home, it’s not the fault of the ballpark.

But that’s not the end of the story. Castellanos is a worse hitter this year than he was in 2018, and while the ballpark isn’t the issue, there is still something going on. Let’s take a look at his wOBA and xwOBA against the four pitches he sees about 80% of the time collectively: the fastball, changeup, slider, and curveball:

Castellanos was a good fastball hitter in 2018. In fact, he should have been a really good fastball hitter, but due to some poor luck, his wOBA against the pitch was only solid instead of elite. In 2019, Castellanos has become an even better fastball hitter, yet he’s still getting unlucky. By weighted runs above-average per 100 pitches, Castellanos is in the 84th percentile among qualified hitters in production against the fastball. He also ranks in the 97th percentile in xwOBA on fastballs.

If you’re a pitcher and you want to throw a heater, there’s no place in the zone to pitch to Castellanos. Here is his exit velocity by zone location against four-seamers:

Castellanos is such a world-class fastball hitter that his average exit velocity in every single part of the strike zone is higher than the league-average generally (91.3 mph), and for each part of the zone:

Unfortunately, the positives pretty much stop there. While Castellanos crushes fastballs, he has not had the same amount of success against anything else. If he did, he’d be in the mix for best hitter in baseball in 2019, and the Tigers would be expected a pretty significant trade return. When looking at the gap between 2018 Castellanos and 2019 Castellanos, it becomes clear where the difference lies: off-speed pitches.

Some of this can be attributed to natural regression. His performance against the curve is the perfect example of this. Castellanos significantly outhit his expected production against curves in 2018, and that performance has regressed to what was generally expected here in 2019. His batted ball data against the pitch looks similar; the luck has just run out.

Against the changeup, things have changed, too. He’s hitting changeups slightly harder this season (86 mph average exit velocity) versus last (85 mph), but his average launch angle has increased by eight degrees, resulting in a spike in popups. 12.5% of batted balls against the change have been popups this season, versus 7.8% in 2018. His line drive rate against the changeup, too, has dropped (39.2% to 18.8%). This season, pitchers have taken the majority of their changeups outside of the strike zone, and Castellanos has taken the bait.

Here is where pitchers are throwing their changeups to Castellanos:

And here is where his swings are concentrated:

Castellanos is clearly swinging at bad pitches. To ascertain just how bad these pitches are, I queried right-handed batters’ results this season against every changeup in the low, “shadow” portion of the strike zone — that is, the zone just outside the heart of the strike zone, the exact place where Castellanos is seeing the majority of his changeups. The league-average xwOBA on similar pitches was just .245. The league-average wOBA was even worse, at .234. That’s not what you want.

Last season, Castellanos got better changeups to hit, and, as he is now, he swung at those.

Here is his 2018 changeup concentration:

And here is his 2018 swing concentration:

Against changeups, Castellanos is doing two things worse this year. He’s swinging at more pitches outside of the strike zone, and when he does make contact, he’s struggling to hit line drives, instead hitting more fly balls and popups.

The slider is where this conversation shifts. In contrast to the changeup, pitchers aren’t really attacking him any differently with the slider, but then, they don’t have to. Castellanos wasn’t a good slider hitter in 2018, and he hasn’t improved in 2019.

Here are Castellanos’ 2019 (left) and 2018 (right) slider heat maps, side-by-side:

Pitchers continue to attack Castellanos low-and-away. That much remains the same. What differs, though, is that they’re attacking him with the slider more often. Notice the six percentage point spike in slider usage from 2018 to 2019. This is significant; it’s roughly equivalent to a 150-pitch increase over a full year. Castellanos has already seen 114 plate appearances end with a slider, compared to just 138 the year prior. If that pace holds, he’ll see between 40 and 50 more plate appearances end against the slider this season than last.

The problem is that there’s no easy fix. It isn’t even as if Castellanos is among the worst hitters in baseball against the slider (his xwOBA is in the 33rd percentile); it’s just that he’s only one of eight hitters league-wide to have at least 100 plate appearances end in the pitch. On a rate basis, Castellanos is seeing the fifth-most sliders among qualified hitters.

The increase in slider usage alone won’t have a significant impact on his OPS; my estimate using 2018 data is that it would be a decrease of about 10 points. It’s Castellanos’ performance against sliders in combination with both his performance on the changeup and regression against the curveball that has resulted in the numbers we are seeing now. Castellanos’ issues run deep, and if he’s going to improve with his hypothetical next team, the “fix” is not going to be nearly as simple as just playing somewhere else.