ESPN College Football

Posted by ESPN.com's Ted Miller

Lost amid all the chatter about USC's quarterbacks -- and Pete Carroll's handling of them -- are a couple of injuries on the Trojans' defense that might cause concern.

Chief among them is two-time All-American Taylor Mays' sprained knee.

Mays didn't play against Washington and is questionable for Washington State's visit Saturday. He's still not practicing and is only doing limited running, which suggests that his knee could remain an issue into next week.

That's important because USC's next foe is No. 6 California on Oct. 3.

Mays was the most important player on USC's dominant 2008 defense. And he's doubly so now. Think his presence might have helped on Washington's game-winning drive last Saturday?

Pause for a moment and tip your cap to Mays' toughness. He sprained his knee early against Ohio State but only missed a few plays and led the Trojans with eight tackles. Ten days later, he still can't run laterally. The loss at Washington was the first game he'd not played in during his career as a four-year starter.

Meanwhile, linebacker Malcolm Smith is questionable with a sprained ankle, though the news on that after Tuesday's practice was better than originally thought.

Ankles are tricky, though, and can linger.

Just as shoulders can for quarterbacks. The idea that true freshman Matt Barkley returns this weekend and everything is just peachy thereafter is dubious.

Now let's push this all into a pile with an eye toward Oct. 3.

USC might face Cal in the Pac-10 game of the year -- if the Bears survive a trip to Oregon on Saturday -- down six starters from its preseason depth chart, a list that also includes receiver Ronald Johnson, defensive end Armond Armstead and cornerback Shareece Wright.

That's potentially four starters from a defense that only welcomed back three starters from 2008.

Of course, Barkley likely will start against Cal, and odds are Mays and Smith will be back.

Still, the likelihood of them being 100 percent is remote.

The preseason story in the Pac-10 was: Is USC vulnerable?

The answer three games in: Never more so.