Robert Woods' health

USC receiver Robert Woods was limited in practice Thursday and didn't participate fully in any of the Trojans' three practices in preparation for Saturday's game against Stanford.

Neither he nor USC coach Lane Kiffin will specify what exactly is ailing him. He has been sidelined by ankle and elbow injuries at various points this season.

"I hope so," Kiffin said Thursday when asked if Woods will play against the Cardinal. "Yesterday he did some stuff, the day before he didn't do anything, so it's just kind of going back and forth."

Kiffin characterized Woods' Thursday participation as "very limited." Woods said he was "full-go." Kiffin's description was closer to the truth, but the truth is that Woods is not in danger of not playing.

He is danger, though, of not being 100 percent -- or, at least, reasonably close to it. And if he isn't, USC is going to feel the effects. The Trojans need him on the field for 60 snaps, functioning well, to have any sort of hope of upsetting Stanford.

He is their only legitimate every-down receiving option.

"Obviously he's critical to us," Kiffin said Thursday. "He's had a great seven games and I think only three or four people have had more catches than he's had at USC.

"That says a lot to what he's done."

Woods has missed other practices this year; it's not like this is his first time. But it's his first time not participating fully in at least one of a week's sessions, according to Kiffin's descriptions, of course. Previously, the Trojans have rested him on Thursday when he's been able to take part in Tuesday and Wednesday's workouts.

"Well, we like to do that when he's had two really good days," Kiffin said. " When he's had two full Tuesdays and Wednesdays where we wear him out and then pull back on him, yea, but when he's only really had one day you don't want to do that.

"So we wish he would have went today, especially because today was so much red zone stuff we hadn't done yet with a normal week."

In other injury news, freshman running back George Farmer (ankle) appears unlikely to playa against Stanford. He sprained his ankle late in Tuesday's practice, was carted off the field and hasn't returned to practice since.

Farmer carried the ball once for 11yards and caught one pass for nine yards in Saturday's win over Notre Dame. He had four carries for four yards and one catch for 14 yards in the previous week's win over Cal.