Tim has posted some interesting notes about the pitches Pedro Alvarez is facing. The gist of it is that he's seeing an extraordinarily low percentage of fastballs and all of his homeruns have come off changeups (three) and curves (one). I have no idea whether his success against off-speed stuff is good or bad. It could be he can't catch up to fastballs and only has the bat speed now to hit slower stuff. If so, at some point he'll start seeing a lot more heat. Or it could be that he's finally adjusting to the pitches he's seeing.
I tend to think that, if he really can't hit fastballs, opponents would realize it by now. If that one scout that Jim Callis quoted could see he had no bat speed left, everybody should be able to see it. That scout's point was that Alvarez has to start his swing so early that he can't adjust to off-speed pitches, but apparently he is adjusting. Apart from the homers, I seem to recall several very long drives to center or left-center that were caught. Scouts aren't always right; in fact, they're spectacularly wrong sometimes. It's possible a scout seeing Alvarez in one of his many horrible games saw a guy who was totally confused at the plate and found a way to explain the struggles that may or may not be correct.
Of course, the scout may have been right, too, and last night's outburst may have been a fluke. I guess we'll find out over the next few hundred at-bats.