Whether Mueller's problems stemmed from that injury of his is to be seen when he comes back eventually.
Personally, I think that other factors were contributing to his lack of production. His knee certainly may have been a factor, don't get me wrong, but I think that we'd be off base to predict another batting champion season out of Mueller. He's a career .291 hitter, and we can expect that from him from now on I think.
True, Youkilis does have a small sample size, and true, he has had some trouble adjusting to major league pitching, but I dont think that pitchers will figure him out. A perfect example of what you said, trot4mvp, is Clemens, who, after dominating the NL, basically fell apart once teams faced him more than once.
I dont think this will happen to Youkilis simply because
a) it hasnt happened yet, and he has faced the same teams more than once
and B ) he's too good of a hitter to fall into that trap.
As of right now, I guess it's a toss up between Mueller and Youkilis. But for the future, I dont think anyone is arguing against Youk.