One of the most common explanations you'll hear for Adrian Beltre and Richie Sexson's slow starts is that they're still trying to adjust a new league that's full of unfamiliar pitchers. Jim Street wrote a feature piece on the subject about a week ago. Hitters don't know what pitches certain guys have, or how they move, and it makes for a difficult acclimation period until they've been around the league once or twice.
Ever the inquisitor, I decided to run some numbers. I compiled a list of 78 hitters who, at some point in the last five seasons, switched to a new league and accrued significant playing time. In this case, "new league" is defined as one in which a batter hasn't played for at least five years (if at all). I pretty much randomly chose this specific time span, but I figure that five years is enough for a guy to forget how certain pitchers throw.
So, the averaged results:
Most recent performance before switching leagues:
.272/.340/.438
Performance immediately after switching leagues:
.271/.339/.442
Look pretty much identical, right? Well, there's that whole "park factor" variable that could be influencing the data, so I'll account for that:
Most recent performance before switching leagues:
101 OPS+
Performance immediately after switching leagues:
103 OPS+
So there you have it - at least as far as the last five years are concerned, moving to a new league hasn't had any deleterious effect on a hitter's performance. While there are obviously extremes at either end of the spectrum, batters as a collective have put up the same numbers after switching leagues as they did beforehand.
Understand that this is not proof that "adjustment periods" don't exist. Even based only on player testimony, I don't see how you could make such a statement - a big part of hitting is knowing the ins and outs of the pitcher you're facing, so it becomes a more difficult task when you don't know that guy on the mound very well. If you were to break down these numbers by month, I bet you'd see that the hitters switching leagues would be worse off for the first month or two after making the move. The take-home message is that these numbers suggest that guys are able to recover after a short while and go on to have their typical offensive seasons. Certainly encouraging, as far as Betre and Sexson are concerned.
It's entirely possible that one or both of these guys won't ever be able to adjust, and the Mariners will pay out the wazoo for a pair of underachieving busted sluggers for the next five years. It's also possible that Albert Pujols could stop producing and turn into a slap-hitter as of this afternoon. The point is, these aren't very probable. It's far more likely that Beltre and Sexson will begin to heat up pretty soon and thrive in the AL, just as Vladimir Guerrero has done after switching from Montreal. You may be getting impatient - God knows we all are - but even Vlad was a .262 hitter after his first few weeks in the league. These things work themselves out over the course of a season, and both Adrian Beltre and Richie Sexson will be the anchors of the lineup before it's all said and done. Save your worrying for a bigger problem.