Young Tiger Nick Castellanos has two seasons under his belt and hasn’t yet turned 24. He’s shown flashes of the talent he was supposed to have as a top prospect, but he’s on the wrong side of the leaderboards so far. The second half had some good news for him, particularly when it came to his plate discipline, but it’s fair to wonder how important he will be for Detroit.

So far he’s been a net negative. Can he turn that around in a big way this upcoming season?

Only five regulars have been worse over the last two years. And it’s worse than that, since most of the guys ahead of him on the list are no longer regulars. Matt Dominguez (released), Billy Butler (DH), Jay Bruce (future DH?), Ryan Howard (future DH / future release candidate), and Dayan Viciedo (released) aren’t good company to keep.

Castellanos is young enough, but Viciedo and Dominguez prove that two or three years of sub-replacement work will quickly erase any optimism about the future. If he doesn’t improve, the focus will quickly shift to wondering if 24-year-old Jefry Marte, coming off his best minor league year or 23-year-old shortstop Dixon Machado, and his patience and defense, can be the answer at the position.

Now it’s time for some good news. There had to be good news or this piece wouldn’t exist, and you wouldn’t read this far. Here’s the good news: only four players in baseball improved their plate discipline as much as Castellanos did in the second half last year.

For most of his career, Castellanos has been a free-swinger, reaching at pitches around 10-20% worse than league average. In the second half, he was league average. He swung less overall. He made more contact. This is progress. The glowing scouting reports on Castellanos on the way up laud his hit tool while saying his plate discipline needs work, so this could be an important change for the hitter, too.

At first glance, it’s hard to see that hit tool, with a hitter who’s striking out a quarter of the time while showing league average power. But Castellanos’ balls in play have been hits 32.4% of the time, good for top 30 in that stat. His hard-hit rate is above-average, too.

I asked lead prospect analyst Dan Farnsworth about this hit tool / outcome discrepancy, and he focused on Castellanos’ hands. Responded Farnsworth:

“His lower half is kind of goofy, so his prospect status was almost entirely due to his feel and hand path. He’s always had fantastic hands, but now he’s a lot smoother with his stride and lower half in general, allowing him to sync up his hands to his hips better. If you watch his stride, he’s staying balanced as he picks up his leg now, rather than last year where it looked like his back hip collapsed as his front leg came up. As a result, his hips look much more efficient driving through the ball rather than seeming to spin around his front leg like last year.”

Here, in a home run swing from August, you can see Castellano’s smoother stride and good use of his hips.

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Put up against his swing in 2009, it’s night and day.

By shoring up his plate discipline and hitting mechanics, Castellanos provides hope for at least one more chance.

Defense is another matter, especially given the usefulness of short sample defensive metrics. His UZR/150 and DRS improved. He’s now middle of the pack on easy plays and unlikely plays. Though his numbers still aren’t great, he’s closer to being a scratch defender and has some standout plays on his register. Even with defense peaking early, it’s not impossible to think a 23-year-old will improve there again in his third season.

The projections have Castellanos improving his defense, walk rate, and strikeout rate in incremental amounts and still ending up short of an average major league player. But improvement is not linear, and these mechanical changes, coupled with a better understanding of playing defense at third base in the pros, might unlock that plus hit tool to do its damage and provide a good all-around young major league player.

Given that he’s the only regular from last year that has this kind of power promise, the Tigers will give Nick Castellanos another shot. Given that it hasn’t gone so well to date, it may be his last shot. Good thing there have been signs that he’s ready to break out.