ENGLEWOOD, Colo. — The cloud of finality that hung over the Denver Broncos as they cleaned out their lockers Monday morning was particularly dark given the uncertainty that shrouded them after their 24-13 defeat to the Indianapolis Colts on Sunday.

With quarterback Peyton Manning uncertain about whether he wants to return for an 18th NFL season and 13 players due to hit unrestricted free agency in March, the window for this iteration of the Broncos to win an NFL championship might have closed.

Manning reportedly played the game with a torn quadriceps muscle suffered Dec. 14 in San Diego. The Broncos listed him as having a thigh injury on the injury reports in subsequent weeks, but he didn’t miss a snap after sitting out a possession at San Diego because of issues related to a stomach virus.

“I know he’s been dinged up for a while,” tight end Jacob Tamme said. “We have a lot of guys that have stuff going on with their bodies. This last quarter of the year especially, it’s like that every year. And 38 years old, I’m sure he hasn’t been feeling perfect for a while. So he’s a warrior, he’s a fighter in football terms.”

Whether Manning returns or not, the Broncos still have to play a demanding schedule in 2015 that includes 11 games against teams that finished 2014 with a winning record.

“If (Manning) is back, that would be great,” running back C.J. Anderson said. “But if he’s not back, at the end of the day, they’re going to put the ball between them lines, and you’ve got to go play.”