The Reds have signed outfielder Nick Castellanos to a four-year deal, or perhaps more accurately "a four-year deal," given the opt-outs after both 2020 and '21, but aside from "what are the Reds going to do with all of these outfielders," there's a pretty obvious question Reds fans have about Castellanos. It has a lot to do with their ballpark -- and how it might affect him.

The thought process goes like this:

1) Castellanos posted a just-OK pre-trade .790 OPS for the Tigers, referring to Comerica Park as "a joke," and claiming to have data showing how much the enormous park hurt him.

Then...

2) Castellanos mashed a 1.002 OPS in two months for the Cubs, saying things like “Hitting-wise [Wrigley Field is a] great park to hit in. I mean, any park is a great park to hit in compared to where I came from, you know?”

Therefore...

3) Now that Castellanos is heading to the hitter-friendly Great American Ball Park, generally considered to be one of the best parks in baseball to bat in, he'll basically be the Aaron Judge of southwest Ohio. Right?

Yes. And no. It never really works out that simply. (Remember that after Giancarlo Stanton hit 59 home runs in 2017 calling cavernous Marlins Park home, he went north to Yankee Stadium's short porches. He's hit only 41 homers in 777 plate appearances as a Yankee since.) But it probably will help Castellanos, somewhat.

How much? We might be able to help try to find out.

How much did going from Detroit to Chicago really help him?

There's no one right way to do park factors. At Baseball Prospectus, looking at only righty hitters, Comerica is sixth-best, Great American 14th, and Wrigley 19th. But at FanGraphs, this time looking at only righty hitters and only for hitting homers, Cincinnati is tied for third-most favorable, with Wrigley tied for fifth and Detroit a middle-of-the-pack 14th.

If that ranking for Detroit sounds shocking, given its reputation and Castellanos' comments, remember that despite the deep center field, there's plenty of evidence that it's a better hitters' park than people think. We detailed this back in 2018, after the '17 Tigers scored 97 more runs at home than they did on the road, theorizing that a favorable batter's eye might help with contact.

Castellanos' own career numbers as a Tiger back that up further. He was better at home.

Home -- .286/.338/.469 -- .807 OPS
Road -- .262/.310/.450 -- .760 OPS

We're trying to get to what Castellanos will do with in Cincinnati, not about Detroit, but the point here is that he's not coming from as helpful a pitcher's park as you might otherwise believe -- and that his late-season run with the Cubs wasn't really about escaping Comerica. (It was mostly about increasing his hard-hit rate from 39% to 47%, and that he's a somewhat streaky hitter who's done this sort of thing before.) That might limit the effect a ballpark change could really have.

What might Cincinnati do for him?

OK, but Cincinnati should still have its benefits, and let's go back to that FanGraphs ranking we mentioned above: "looking at only righty hitters and only for hitting homers, Cincinnati is tied for third-most favorable."

That's maybe a bigger deal, because Castellanos just hit 58 doubles, the 10th-most in a single season ever. The year before, he'd hit 46 doubles, the fifth-most in the Majors that season. That speaks somewhat to the type of hitter he is; over the last three seasons, Castellanos has the fourth-highest line-drive rate among the 308 hitters with at least 500 batted balls, but only the 152nd-highest fly ball plus pop-up rate.

That means that he's not exactly lofting a ton of back-spinned balls over anyone's fences, but we can try to see how many of those might have become homers if they'd been hit in Cincinnati. But first of all, we're not talking about 58 doubles, because 24 were hit on the road, and he still has to play road games. And we're not talking about the the remaining 34 home doubles, because some -- see this one, or this one -- were blooped or pulled down the line past the third baseman.

So instead, we'll do this. We'll look at all batted balls he hit at Wrigley or Comerica in 2019 that went at least 300 feet, and which would have been home runs in at least one Major League park, based on 3D trajectories from Statcast that take into account both wall distance and wall height. (This is not currently attempting to adjust for wind, elevation, etc., but people like to call Comerica "enormous" and Great American "a bandbox," so this is a good start.)

There were 11 of those balls in Detroit, and 14 more in Chicago. Here's how the 25 broke down in reality:

Home runs: 9 (1 Comerica, 8 Wrigley)
Doubles: 7 (2 Comerica, 5 Wrigley)
Outs: 7 (6 Comerica, 1 Wrigley)

The question, then: If all 25 of those balls were hit in a ballpark shaped like Great American Ball Park, would the outcomes be different? We looked at all 25, and here's what the estimated outcomes would have been:

Home runs: 15
Non-home runs: 10

Six more homers! That's seemingly a big difference -- though there is a catch, as we'll get to in a minute. (It's difficult to know if a ball that stayed in the park would have been caught or not, so we'll lump those together for now.) Where did those six come from?

Four of them came from Detroit, three that had been outs, and one double. While Comerica probably didn't impact Castellanos as much as he thinks, you can certainly see what he was talking about on this July 6 flyout to right-center, a ball that was mashed at 101.9 mph off the bat and was projected to go 402 feet. Jackie Bradley Jr. made the catch look easy.

Or imagine this April double against the Royals. This wouldn't have gone out of every park, actually, just 16 of the 30. Great American would have been one of them.

But it wasn't just Detroit, because two of them came at Wrigley, where an August flyout and this August double likely would have been out of Great American.

So would he have found a few extra dingers calling Great American home all year? Yes, probably. But ...

So what's the catch?

Cincinnati sure seems like it's a better fit. But what's the catch? A few things, to start with. First of all, "hitting home runs" and "park effects" aren't exactly the same thing, and we haven't attempted to capture the full park effects here. We're not trying to account for cold Detroit springs vs. hot Cincinnati summers. Most of all, we can't just assume that the way he mashed for the Cubs is just who he's going to be going forward. Remember, we said he hit 11 of those "at least 300 feet and a home run in at least one park" balls in 439 plate appearances for the Tigers (one every 40 plate appearances), and 14 in 225 for the Cubs (one every 16 plate appearances). That's probably not likely, or predictive.

Ultimately, this all comes down to Castellanos, and what kind of hitter he is, because we have one last thing to show you. One of the more powerful Statcast metrics attempts to take out the effects of defense and, fortunately for us, ballpark, by focusing on quality of contact and amount of contact. That is, it grades hitters based on how hard and how often they hit the ball, and not about whether a great fielder or a helpful ballpark added or subtracted. It (xwOBA) is on a scale similar to on-base percentage, and in 2019, the range went from .455 (Mike Trout) at the top to .251 (Nicky Lopez) at the bottom.

With the Tigers, Castellanos posted a .336 mark, ranking 127th of 282 with 200 batted balls.

With the Cubs, Castellanos posted a .418 mark, the fifth-best of 84 with 200 batted balls.

Remember, that's all about the point of contact, and nothing about how the park helped or hurt. With the Cubs, he was just ... better. This is it. This is the entire thing right here. He didn't perform better because of his new home, he performed better because he was.

Whether that's a well-timed hot streak or pure joy at getting out of last place or just Castellanos thinking the new park was helping is unclear, obviously. Maybe it's a combination of all of it.

If he hits like he did with the Cubs, it won't matter which park he calls home. If he hits like he did with the Tigers, he'll maybe get a few extra homers, but the end result will still be "just OK." Our guess is that the answer is in between, that he'll be the same "20% or so above league average" hitter he's been for the last four years. It would have made him Cincinnati's second-best hitter in 2019. For a team hoping to contend, that's a big deal -- no matter where he calls home.