I was just watching a bit of the Cubs' vs. the As, during the BB commercials, and they mentioned that Zambrano apparently worked out quite a bit and lost 20 lbs in the off season.
I'd vote for him as well. Wolf had a few more K but Zambrano's ERA was over a whole point lower than Wolf's last year. He's got a much more substantial jump in offense behind him this year too. The Phillies are looking tough but the Cubs appear to have finally put together a top notch team. Not that I'm biased or anything!!
Zambrano, Piñeiro, Miller, Wolf, as far as those guys are concerned. I think ERA is the best 'one stat' number but if you look at the other numbers, they kind of follow ERA.