ENGLEWOOD, Colo. -- Denver Broncos center Tom Nalen tore his right biceps muscle and will be out for the season.

The five-time Pro Bowler was injured in the first quarter of a 41-3 loss to San Diego on Sunday, but kept playing.

"He played the whole game with a torn bicep, and not many guys will do that. We couldn't even run inside running plays, had to run outside running plays," coach Mike Shanahan said Monday. "He didn't have any strength in there. It kind of gives you an idea of what he's made of."

The Broncos also lost tight end Nate Jackson for the season with a torn groin. Cornerback Champ Bailey, who injured his left quadriceps against the Chargers, should be ready for the Pittsburgh game on Oct. 21. The Broncos have a bye this week.

"If we were playing this week, I don't think he'd be able to play," Shanahan said. "He should be fine for Pittsburgh."

Shanahan said he didn't want to discuss who would start in Nalen's place, saying filling the void will be difficult.

"I have confidence in a number of our players. You've got to prepare for that, even though you don't like to. We have a couple guys who could fill that void," Shanahan said.

Chris Myers is listed as the backup on the Broncos' depth chart.

"Tom, I believe, is the best center to ever play the game," Shanahan said of the 14-year veteran. "That's what I believe."

Nalen is expected to have surgery within a week and will be out for close to four months. Shanahan didn't think the injury was career ending. "He should be fine and ready to go next season," Shanahan said.

Nalen is the second starting offensive lineman to go down. The team lost guard Ben Hamilton to a concussion in training camp. He was placed on season-ending injured reserve on Sept. 28.

Nalen hasn't missed a start since tearing a ligament in his left knee against Kansas City on Oct. 20, 2002. He had surgery to repair the knee and was back 10 months later in time to start the 2003 season, during which he earned his fifth Pro Bowl selection.

"Anytime you lose a great player, it hurts you. That's part of the National Football League; guys have to step in and fill the void. Losing a guy like Tom Nalen is a big blow to our football team. He was a captain and a great leader. He just said it was a little sore, but he knew he tore it early. That gives you a little idea about his mental toughness and what he brings to the table," Shanahan said.