Alexi Casilla has been great so far this year for the Twins, but can he keep it up?

First, let's look at what he's done in the minors:

.270/.346/.348 -- age 19, Rk/A
.311/.378/.383 -- age 20, A/AA/AAA
.318/.385/.398 -- age 21, A+/AA
.269/.345/.344 -- age 22, AAA
.219/.350/.250 -- age 23, AAA (2008)

.293/.367/.366 -- overall

Since Casilla came up and got a cup of coffee two years ago, I think it tends to get lost in the mix, but Alexi Casilla is really young. Delmon and Gomez are younger, but not in a meaningful way.

Casilla has also been asked to play for a lot of different teams in a lot of different places in his rather brief career. That certainly happened a bit more with the Angels than it did with the Twins (one side effect of their patience with prospects is that you basically never look back and say that they jerked a player around between levels in the minors), but it still happened.

Last year seemed to be something of a step back for Casilla, but it wasn't really that bad of a year when you adjust for factors like: age, position, and sample size. Yes, overall it was about 550 PA (and about the worst 200 PA of his career when he was with the Twins), but in the scope of a career, 550 PA is not that much (and 200 PA is especially miniscule within that scope.) The list of players who have struggled to hit in the majors when they are 22 years of age is a long one, filled with both distinguished and undistinguished players, so I don't know that that really helps us to judge him any more than his ~200 PA this year helps us to judge him.

Getting back to his minor league performance--through all of the level switches, when you look at the aggregate numbers, he's been able to hit for average. A .293 average for that age at those levels is nothing to sneeze at, and with just 178 strikeouts against 158 walks in 1686 plate appearances, mixed in with some speed, hittng for average looks like a sustainable skill for Casilla.

Casilla's walk rate has also been above average, though not completely stellar. As long as he can hit for a high average, though, pitchers will be careful enough with him that he should be able to keep up a reasonable walk rate.

Alexi hasn't had much power. That's a negative, and with the low strikeout rate, it seems unlikely that he'll develop anything more than gap power. On the other hand, I've seen Billy Beane quoted as saying, essentially, that good hitters can become power hitters but power hitters don't become good hitters. The idea is that power tends to be one of the last tools to develop and if you hit for a high average, you're probably good at making contact, and those hits might eventually go for more bases, but if you're not good at making contact, you can't usually develop that skill. So there's a chance that Casilla could hit for a ~.150 ISO in a couple of his peak seasons. That's not Ruthian, but it would be Alomarian. Either way, power or no power, he's a middle infielder so it's not a huge concern if he can continue to get on base.

From a fielding standpoint, I just don't know what to make of Casilla at this point. It's tempting to think that his speed should give him good range, but he also doesn't seem (to me) to have great hands and in the past he's been prone to making silly mistakes. I'm essentially pleading not enough information here, but in the absence of more information, I'd say that he'll probably wind up being closer to average than he'll be to great or terrible.

Overall, I look at Alexi, and I see a guy with a better track record than Luis Rivas. I know that doesn't carry a lot of weight with Twins fans, but Rivas wasn't as bad as he was made out to be. He was a replacement level player who got essentially replacement level dollars. Rivas never really helped the team win, but he wasn't actively hurting them either. (And the Twins did manage to win a lot of games with Rivas around.)

So it seems completely plausible to me that Alexi can be an above replacement level player on a yearly basis. Just how far above replacement level is tricky to say. The tools are there for him to be a borderline All-Star (or even a full-fledged All-Star) every now and then--in the same way that Luis Castillo was a borderline All-Star some years and managed to actually make the team 3 times--but there are enough question marks that you wouldn't want to count on it.

I don't expect Alexi to hit .321/.366/.455 for the rest of the season, but .290/.350/.375 seems like a reasonable expectation to me. Going back to Luis Castillo, he hit .323/.383/.395 in the second half of 2006. The gap between that performance and my expectation for Casilla is not that big.