Weaver, Wainright, and Lackey. Weaver is having an awesome season and I don't think that many people realize it. I don't trust Lackey at all right now.
I like Wainwright best of the three. If anything, I'd be selling high on Weaver as he's benefited well from solid defense. It's hard to make sense of Lackey right now, more or less because he's either been shy in throwing certain pitches (curve, changeup) or just simply easing into his comfort zone.
Weaver (By a decent amount), Wainwright, Lackey. Weaver is your best choice as he is behind a great offense and throwing the ball very well. Wainwright is a solid all around pitcher. Lackey is simply not living up to expectations this year.