The problem is though that time, and with time, repeated at-bats, really will tell. Many pitchers, especially when switching leagues, often benefit from the extremely limited exposure to either AL or NL hitters. In Matsuzaka's case, neither the AL nor NL has seen him in action, except in very limited cases at the World Baseball Classic and in Spring Training.

I agree, you have to concede his first outing went about as well as could be expected, no doubt, and I think he probably is a very remarkable pitcher. But like you said, time, and scouting reports, and repeated viewings, particularly in the unfriendly pitching environment of the AL, can change the way a pitcher performs over the course of a season, and ultimately, a career.