I'm a huge fan of September roster expansion. Good teams can use the extra bodies to give key players ample rest going into the playoffs, while bad teams can get creative with prospects. Many a fringe prospect has used September games to become surprisingly prominent (looking at you, Dusty Ryan). But fans are usually more excited about expansion than managers are. Leyland has previously noted that he doesn't like having extra guys in the clubhouse just for the sake of it, so projecting those extra guys tends to be a conservative exercise. Of course, the question on everyone's mind becomes: would Nick Castellanos be seen as a contributor, or is he just an extra guy?
Bryan Holaday, C: A 3rd (or 4th) catcher is the most automatic addition imaginable. Throughout most of the season, teams are loathed to PR or PH for catchers, or use good-hitting catchers as DHs/PHs, knowing that an injury or ejection could leave them with a dreaded "emergency catcher." Of course, the Tigers have the most professional, charming, and handsome emergency catcher around, but still, we'd all feel a lot better about turning to an actual, full-time catcher. Holaday is a backup's backup for a reason; he doesn't do anything better than Avila or Pena (except run, maybe). But a flexible roster is a better roster, and Holaday will serve as a much-needed safety net. During both Avila DL stints, Holaday was the choice, so there's no reason to expect differently.
Hernan Perez, IF: Backup infielder is another one of those additions that's pretty automatic. Once again, the guy with earlier experience this year is the obvious choice. Perez is probably a better backup than Santiago right now, and at the very least, he'll be the best runner of anyone on the team. Infante and Iglesias probably won't be taking many days off, and Santiago will still get some playing time, but Perez could play short and push Iglesias to 3rd on days Cabrera rests his injured self. Otherwise, expect him to see a lot of pinch-running duty.
Phil Coke, LHP: Don't even act like you don't know this is coming. Regardless of how bad he's been, and how little they really need a LOOGY when Veras and Benoit can blow away LHBs, there is simply no way the Tigers will send him home once Toledo's season ends. Plus, Leyland already said he'd be back on September 1st. What he'll do once he gets to Detroit is less obvious, but since there aren't any other lefty relievers who have stood out (even Smyly has struggled against LHBs this month), I'm guessing he goes back to a little long relief and a little one-batter work. Do I expect him to be actually be any better than he was before he was sent down? Not at all.
Octavio Dotel, RHP; He's not a true September call-up, since his job would be returned to him after an injury rehab anyway. But the expanded roster makes his return all the more convenient. The only obstacle then becomes his actual health. He's made 8 appearances in August, but hasn't really pitched well. Reports on his stuff has been mixed as well. If his arm isn't in actual pain, the Tigers will call him up in September to test him against major leaguers, and hopefully he'll show himself ready for the playoffs.
Jose Ortega, RHP: Ortega flashed some really electric stuff in his earlier time in Detroit but struggled with command (stop me if you've heard that one before). In Toledo, he's been completely untouchable. In 48 innings of Triple-A work, Ortega allowed only 25 hits, striking out 55 and posting an ERA of 1.69. 33 walks are a blemish, to be sure, but given the issues the Tigers have had with long relief, they could really use another one-inning flamethrower.
Darin Downs, LHP: There's very little flashy about Downs. The stuff doesn't stand out, he was bad in Detroit, and his subsequent injury didn't really allow him to re-establish himself in the minors. But he has succeeded in the past, and the Tigers desperately need a left-handed arm to show up before the playoffs.
Evan Reed, RHP: Much like Downs, there's little about Reed that sets him out from the crowd. While all the Tigers lefties are feel guys in the low 90s with average command, all of the Tigers righties are big arms with no command. I'd rather see Ortega get innings than Reed, and Putkonen just seems like a better version of Reed to me, and he already got called up. But at the very least, Reed is on the short list.
Jose Alvarez, LHP: Obviously he's in the picture because he has experience and a left arm used to throw baseballs, but his bullpen experiment was a disaster. As a long-reliever, there are better options, so Alvarez will probably go home for the winter. However, if a starter has to miss a turn, Alvarez will get the call.
Melvin Mercedes, RHP: I could see the big righty getting called up as a reward for a strong season. Across two levels, he's posted an ERA of 0.90 in 50 innings. As more of a sinker/slider guy than a traditional big-armed Tigers RHP, the Tigers might be interested in testing him as a different look. Unfortunately for him, there are probably too many arms ahead of him.
Danny Worth, IF: I don't know what Worth would actually do around here, but it just feels like he should be up in September, doesn't it?
Nick Castellanos gets his own heading:
He's been the name on everyone's mind for the entire season, so it seems almost unfathomable that he would be kept off the roster the entire season. But the more I look at the way he's played and the way the Tigers have handled the outfield, I don't see many compelling reasons for him to be promoted. The Tigers have five outfielders already, making it already fairly difficult to distribute regular playing time. Dirks, Kelly, and Tuiasosopo aren't playing great, but they're still going to be on the roster, and probably on the playoff roster.
For his part, Castellanos has been good in Triple-A, but it's more of a "this is a really strong showing for a young guy in Triple-A" good, and less of a "he really needs to be in the majors" good. His status is further complicated by being off the 40-man roster. There are 39 players on it right now, but if Dotel gets activated, they'll need to give him that spot. Luis Marte could be shifted to the 60-day DL to open a spot, but then they might need that spot for Jhonny Peralta.
On the other hand, there aren't many compelling reasons to keep him off the MLB roster, either. Castellanos is ready for the challenge of MLB pitching, and while I don't think he'd excel right away, I don't think he'd embarrass himself. So what if Don Kelly or Andy Dirks misses a start? As far as the 40-man, they could probably release Danny Worth without anyone even noticing. Once the IL season ends, he won't have anywhere to play.
The last point being the most significant, I'd wager Castellanos does get promoted this season, right after Toledo finishes theirs. Once in Detroit, he'll probably spend most of his time watching everyone else, getting maybe 12 games before the end of the season. Is that a little anti-climactic for prospect watchers? Absolutely. But prospects take a back seat when the big club has the best lineup in baseball.