FWIW, Tito and Gonzo both said they expect him to play today, so hopefully that's the case. The thing is, it was just nagging at him all game. It wasn't like it was one play where he dove or slid or something and he hurt it. The last play he was in, he hit a HR and trotted around the bases.
That leads me to think that it's just a minor injury, taken out for precautionary reasons, which is consistent with everything they are reporting. I don't think he'll miss a game this series, purely based on their comments and the events around the injury.
As far as Youk, you're right. The guy is killing us on both sides of the ball right now. Love him for his drive, but he's a max effort guy, and when he can't give you max effort, he's not effective.