Since Webb pitches on Wednesday, Tim Lincecum is scheduled to pitch on Sunday, and Edinson Volquez is projected to start Saturday, I think there is a good chance Webb starts for the NL, even though I don't think he deserves to over Lincecum or Volquez.
I will say it again. Webb starts tomorrow, not Wednesday and he will pitch again on Sunday. Melvin has reversed he and Owings in the pitching rotation so Webb can get two starts before the All Star game.