I am working up a big post on Oliver, but since his drop in velocity was in the news today, I figured I would excerpt the relevant portion today.
Metsblog relayed an article by Matthew Carruth over at fangraphs today pointing out that Oliver Perez was among the "leaders" in velocity lost off their fastball between 2008 in 2009. Oliver's fastball was 1.2 mph slower in 2009, which was the 15th biggest loss in baseball.
Matt Cerrone had this to say about that finding:
…i have to think that is mostly because of his knee, and not being able to get the right pivot off his front leg…I could not agree more with this.
I am very tough on my Mets, but I think I am fair, and I feel very strongly that Ollie's struggles last year are legitimately because of injury. Sometimes a guy just sucks and blames it on injury - but I don't think that is the case here. And here is why:
In addition to having the slowest average fastball of his career (90.0, down from 91.2 the year before) his changeup velocity was UP almost five MPH. His average changeup went from 80.1 to 84.9. At that speed, there is only 5 MPH separating the changeup from the fastball -- a useless gap.
In order to be effective, a changeup has to be at least 8 to 10 miles per hour slower than the fastball. For reference, the gap between Johan Santana's fastball and changeup was 11.2 MPH in his 2008 season. Oliver Perez had a 9.4 MPH gap in his successful 2007 season.
He was all out of sync, and it was something physical or mechanical - he wasn't just terrible for no reason. The excessive zip on his changeup is proof of that. If he's healthy, I think his fastball bounces back to where it used to be.
I really think Ollie can come back strong in 2010. Check back here at Fonzie Forever for more on this in the next few days.
 No citation on this, so someone can point me the right direction if they like. I know I've read it but I'd rather be safe than sorry before I get some random rumor floating around the interwebs.