The youngster batted .360 with six walks, two doubles, one home run and six RBIs in 15 games during Grapefruit League play.
The Tigers sent Castellanos down to Triple-A Toledo not so much so he could work on his hitting, but so he could continue to develop as a left fielder. Castellanos came up through the system as a third baseman.
"What (manager Jim Leyland) said is when the rest of your game looks as comfortable as you do in the box, then you'll be up here," Castellanos said during the Mud Hens' last home stand. "Obviously at that time, I swung it really well in big league spring training, but he's talking about playing defense, running the bases, picking up signs from the coaches, just everything, being a complete baseball player."
Currently, Castellanos is playing left field every day and learning how to adjust from Double-A Erie to Triple-A.
"Double-A to Triple-A is a little bit of a jump, just as the next level is, and there’s going to be an adjustment process with every level," Mud Hens manager Phil Nevin said. "I think he’s handled it well so far. He’s definitely come ready to play each day, he’s come ready to work.
"Very well could have four or five more hits, balls that he’s hit right on the screws to right, balls where the wind was blowing in. He’s done a fine job."
Through 19 games, Castellanos was batting .230 with five doubles, a triple and five RBIs in 19 games.
The Florida native admitted it's not easy playing in cold weather, even though he did have some experience doing so with Single-A West Michigan in 2011. Plus, pitching and defense are both better at this level.
"A lot of guys in lower levels, when guys will throw balls it will be by a noticeable amount, so you don't even have to bite at it," Castellanos said. "A lot of times here when they'll throw balls, they're missing the plate by a couple inches or they're missing down by a couple inches, so a lot of times early in at-bats, I'll get myself out with those pitches instead of getting ahead in the count and then driving something that's my pitch.
"The strike zone is different here than it was in the lower levels, it's a little bit smaller than it was in Double-A. So it's just another aspect of the game that's going to be an adjustment. And when I get to the big leagues, it's going to be another adjustment."
Castellanos said it's taken him a little bit to adjust each time he's been promoted to the next level.
"If you look back, the only level that really I didn't need an adjustment period in the beginning was in Lakeland," Castellanos said. "West Michigan, I had a little bit of a slow start as I got used to everything, also in Erie. I had about 15 or so games where I wasn't hitting too well and after you start getting used to your team, used to your surroundings and get comfortable in your lineup, then everything starts rolling."
Nevin said Castellanos, who just turned 21 and is already 6-foot-4 and 210 pounds, is still growing physically.
"When I watch him, he’s going to be a home run hitter in the big leagues," Nevin said. "He’s going to hit for average, but he’s going to hit home runs. He’s going to hit 25-30 home runs in the big leagues.
"You can’t teach a guy to hit the ball to right the field the way he does. It’s a feel. He has that."
Castellanos has also been working diligently on his defense in left field. The first thing he's had to get used to is being prepared even if he doesn't see a ball come his way for a few innings. It's a different reaction than he had at third base.
"It's easy to get distracted and it's easy to think about your at-bats or whatever when you're in the outfield, instead of focusing on the hitter because at third base if you're not focusing on the hitter, you're going to eat one," Castellanos said. "In the beginning, it was a little more difficult for me to keep my concentration but now it's just becoming second nature, just because of the amount of games I'm playing out there."
Nevin said he had the same problem when he made that move as a player so he's been able to help Castellanos. Also lending a hand when he can is Quintin Berry.
"I’ve seen him get better," Berry said. "He’s picking his spots, making the routine plays, not trying to do too much. I talked to him earlier, when we first got down here, said I was going to try to work with him. But they’re doing a lot with him, taking him out there and getting him work. Long as he hits, he’ll be all right."
It seems likely that Castellanos will be playing for the Tigers by September at the latest. He just wants to make sure he remains in Detroit.
"I think they've said it time and time again, when I get there, they don't want me to be a guy that goes up and down, they want me to stay there," Castellanos said. "So in order for that to happen, I have to do everything up to their expectations."