It just looks like he has nothing left. I don't mean to make excuses for the guy (who, by the way, was really the only pre-season prediction I was off the mark with) but facts are facts.
I look at the Upton at bat tonight as a microcosm of what Perez has become. He got ahead 0-2, with one of the strikes a well-struck foul ball. Then? He had nothing to finish with. After trying to back-door two slurves to Upton and running the count to 3-2, it looked like he had just no desire whatsoever to challenge the batter. He had nothing to challenge him WITH.
The Montero at-bat was similar. After getting Montero 0-2, he nibbled around. He no longer has the velocity on the fastball to beat people, and without it, the slider just isn't effective. Batters appear to be "on" his pitches. And why the experimentation with the silly side-arm motion?
It's hard to say, as a casual observer, if this is exactly the case. I don't know what is going on in the mind of Oliver Perez, and if he's really lost faith in his ability to challenge hitters. But I do know that when a pitcher loses a couple ticks off of their fastball, and doesn't have a diverse repetoire (a third pitch), that the pitcher is in big trouble. I do also know what it feels like to have two strikes on a batter and have NO IDEA what you can throw to finish him off, because he's better than you.
That's really what it looks like with Ollie. And for that, there's no remedy.