Ernie Sims practices at middle linebacker

IRVING, Texas -- Though coach Jason Garrett didn't give it a full endorsement as yet, Ernie Sims has emerged as the starting middle linebacker with Sean Lee out with a hamstring injury.

Sims has played extensively at the weakside and strongside linebacker spots so he's still learning the middle.

"That's what we're looking at," Cowboys defensive coordinator Monte Kiffin said Wednesday. "We're looking at this whole thing."

The Cowboys' defense is shuffling players after injuries not only to Lee but Justin Durant (hamstring) as well. Defensive end Kyle Wilber got some looks at strongside linebacker during Wednesday's short practice at Valley Ranch. Kiffin is still experimenting just to see if Wilber, who was drafted as an outside linebacker last season, can play the spot.

Normally a middle linebacker makes the signal calls, so Sims can do that. But Derrick Brooks, the standout weakside linebacker, called the signals for Kiffin in his days with the Tampa Bay Buccaneers, so the Cowboys could call on Bruce Carter, too.

Sims said there are some challenges with playing the middle linebacker spot over the other outside linebacker positions.

"The outside linebackers are more edge players," Sims said. "There more space players. But in the same breath, it's a different feel. There are different techniques. Outside 'backers are totally different from the inside 'backers techniques. When it comes to the [weakside] and [strongside] linebacker roles, I'm very comfortable with those. I've been doing those for so long, my keys are on point. It all goes back to me having to talk to Sean and asking him and get into his mind what his keys are and what he's keying on particular plays."