IRVING, Texas -- Sean Lee's season is over.

The Dallas Cowboys announced they are placing the inside linebacker on season-ending injured reserve with a toe injury and have signed veteran linebacker Ernie Sims to fill his roster spot.

Lee will have surgery on his right big toe next week with a full recovery expected for 2013. Running back Felix Jones had a similar surgery in 2008 and has not had any issues with the toe since.

Coach Jason Garrett said the team initially believed Lee would miss 4-6 weeks with the injury, which was suffered in the third quarter Sunday at Carolina, but a second MRI on Tuesday confirmed extensive damage.

Lee's agent, Mike McCartney, said Wednesday morning that Lee would be seeking a second medical opinion, but that the linebacker suffered a "significant tear."

"We're not hopeful," McCartney added. "I'm sure he's having surgery sooner rather than later."

Lee leads the Cowboys in tackles with 77 in the first six games, according to the coaches' film. He has two tackles for loss, eight quarterback pressures, one interception, two pass deflections and a forced fumble.

"Injuries are part of the NFL, as you know, in Dallas and 31 other cities," Garrett said. "We've had them. Everybody's had them. You have to deal with them through the season.

"Sean Lee is an outstanding football player. I can't tell you how well he's been playing since he's been our starting inside linebacker. He's the leader of the defense. He makes the calls. He plays the right way in practice. He plays the right way in the game. He defends the run. He defends the pass. He's a bell cow for us and a guy that really, really everybody on our defense and football team looks up to. He goes about it the right way and he's an outstanding person as well. We love everything about him. It's obviously unfortunate and disappointing that he had the injury."