In one sense, Detroit third baseman Nicholas Castellanos has been one of baseball's more impressive hitters this year. Based on the expected outcomes of how hard he hits the ball and how often he makes contact with it (we'll explain in a second), the skill he has shown at the plate puts him in the top 15 percent of all hitters with at least 100 times to the plate. Castellanos has been better than Gary Sanchez, Eric Thames and Daniel Murphy. He's been a star.
In another, far more real sense, Castellanos has struggled badly. He's hitting just .230/.309/.396, a line that's 10 percentage points below league average, one that doesn't crack the Top 200 of all hitters with at least 100 times to the plate. Castellanos has been worse than Nick Ahmed, Timothy Beckham or Allen Cordoba. He's been a mess.
So which is it? And is there something in there that shows why the Tigers still have hope for a turnaround, despite the uninspiring performance? The answer is "yes," and we might have already seen the signs of a turnaround over the past week.

When we say "expected outcomes," what we mean is that there's a difference between hitting .230 because you're simply not a strong hitter and hitting .230 because batted balls just aren't falling for you in the way they ought to be. One of those hitters probably stays at .230 all year, and the other may be expected to find more success as time goes on. But how can you tell the difference? We've made a great deal of progress on that front with Statcast™, and it's good news for Castellanos.
Here's what we mean. By looking at how hard a batter hits the ball (exit velocity) and in what vertical direction (launch angle), we know a great deal about how likely that ball was to turn into a hit, and we know a great deal about the batter's skill. For example, when Castellanos squared up a ball at 105.9 mph that went 422 feet on May 18 against the Orioles, he smashed a ball that turns into a hit 95 percent of the time. Once the ball leaves his bat, it's out of his control, so the point here is to credit him for showing the great skill required to crush a Major League pitch 422 feet, regardless of whether it turns into a hit or an out due to factors he doesn't command. (On that day, an out, thanks to Adam Jones and Comerica Park's deep dimensions. On many other days, a home run.)
If we know how likely each batted ball is to turn into a hit, then we can see which hitters are having high-value batted balls turn into outs. For example, what about all batted balls that had at least a 50 percent probability of becoming a hit (or a .500 expected average, if you prefer), but didn't actually become hits?
Most outs on batted balls with a 50 percent or higher Hit Probability in 2016
24 -- Nicholas Castellanos, Tigers
23 -- Robinson Cano, Mariners
23 -- Kyle Seager, Mariners
23 -- Jose Abreu, White Sox
23 -- DJ LeMahieu, Rockies
That's a lot of value turning into outs. That's a lot of lost production for Castellanos. Take, for example, this 110.5 mph line drive that turns into a hit 83 percent of the time, except when Francisco Lindor leaps to make a fine grab:

Or this 75 percent Hit Probability batted ball robbed by a diving stop from Chicago's Todd Frazier:

Castellanos had had 24 of his 160 batted balls (15 percent) turn into outs on balls that should have been a hit more than 50 percent of the time; for comparison's sake, Kristopher Bryant has had that happen just five times in 164 batted balls (three percent). Zack Cozart has had it happen only four times in 158 batted balls (2.5 percent). It happens to everyone, but it seems to be happening to Castellanos more than anyone.
We can show that even better on a seasonal basis. If you do that for each plate appearance, and include real-world strikeouts and walks, what you can do is find a hitter's expected seasonal performance. Instead of using batting average, which ignores extra-base hits and walks, we prefer Weighted On-Base Average (wOBA), which is very similar to On-Base Percentage except it gives increasingly more credit to extra-base hits as opposed to treating every time on base equally, as OBP does. (The 2017 Major League average wOBA is .318.)
While that sounds complicated, it's really not. It's basically looking at a hitter's quality of contact, knowing he controls that fully, while he doesn't control opposing defenders or ballparks. If you look at the comparisons between Castellanos' actual and expected outcomes, you see something wild.
Last year, Castellanos' expected wOBA was .379. That's very good, 27th of the 429 hitters with 100 plate appearances, better than Anthony Rizzo or Bryce Harper. Though his actual wOBA of .354 was slightly lower, it was still in the top 20 percent, better than Matt Kemp or Buster Posey.

This year, Castellanos' expected wOBA is .378, basically identical. That's also very good, 33rd of the 277 hitters with 100 plate appearances, better as we said than Murphy or Sanchez. But his actual wOBA is just .311, which means that even though he's making similar contact to last year, his production has dropped by a full 43 points. Overall, the 67-point difference between Castellanos' expected and actual production is the second most of any of those 277 hitters, behind only his teammate Jose Cabrera . 
Now, it's not a coincidence that two Tigers are at the top of the list; it's actually three of the top five, since James McCann ranks highly as well. We've talked a lot about what the deep center field in Comerica can do to Detroit hitters, turning extra-base hits into easy outs. But only 14 of the 24 high-value outs we discussed before came at home, and overall, Castellanos has been better at home (.276/.377/.467) than the road (.190/.244/.331). This isn't all about the park.
It's true that Castellanos is going about this a little differently than last year, because his hard-hit percentage (95 mph exit velocity or higher) has gone up from an above average 38.7 percent to an elite 49.4 percent, which is again one of the best numbers in the game. Though he's hit more balls on the ground this year, which is part of the problem, he's also hit just two pop-ups, which is outstanding.

If you look at that list of hard-hit leaders, you'll see studs, guys like Aaron Judge and Miguel Sano, and hard-hitting Tiger teammates like Cabrera, J.D. Martinez and Alex Avila. It's truly difficult to hit the ball that hard and not find success from it. He needs to get the ball off the ground, but mostly he needs to have just a bit better luck with those high-value batted balls.
Over the past two weeks, Castellanos is hitting .265/.357/.449, a .350 wOBA. By itself, that doesn't mean much. In conjunction with what we know about his hard-hitting skills, it may just mean the tide is turning.