You mean like how Hideo Nomo fell on his face the rest of his rookie year?
191.1 ip, 124 hits, 14 hr, 78 bb, 236 k, 13-6 record, 2.54 era
Oh, not that year...you mean his next year.
228.1 ip, 180 hits, 23 hr, 85 bb, 234 k, 16-11 record, 3.19 era
Yep, he fell flat on his face after he 'looked good for a few games'.
Every pitcher is different. Just because Matsuzaka happened to pitch in the Japanese league doesn't automatically mean he can't be a very successful major leaguer any more than it means he's destined for the Cy Young. It means he faced BETTER competition in the equivalent of his time in the minor leagues and now he's a very polished 26 year old rookie. We'll see what he can do over the course of the next 6 months.