ENGLEWOOD, Colo. — The Broncos are placing quarterback Joe Flacco and linebacker Corey Nelson on injured reserve, Head Coach Vic Fangio announced Friday.

The Broncos are promoting quarterback Brett Rypien and linebacker Josh Watson from the practice squad to the active roster in corresponding moves.

Flacco (neck) and Nelson (biceps) both suffered injuries against the Colts, and Head Coach Vic Fangio previously ruled Flacco out for Sunday's game.

"At best, it was six weeks where he could do nothing," said Fangio on Friday when asked why the Broncos decided to move Flacco to IR. "When I say nothing, [I mean] absolutely nothing. So he would need probably two weeks to get back. And [it's a] good chance it would be eight [weeks] of doing nothing and then another week or two to get ready. So you guys can do the math. So it kind of became an easy decision."

Brandon Allen will start at quarterback, and Rypien will serve as the team's backup. Neither player has seen snaps in a regular-season NFL game.

Despite his injury, Flacco has remained involved in meetings this week to assist both players in their preparation.

"He's been in meetings all week," Fangio said. "I didn't have him come out to practice this week, but he might be out to practice some in the future."

Fangio said Flacco's overall mood and demeanor has been "good."

"I mean, he's not happy about it obviously," Fangio said. "He's kind of surprised, because he really doesn't feel that bad. The doctors are surprised he's not feeling worse based upon the MRIs and the tests, etc. So he's frustrated [and] down a little bit, but he's a pro."

In eight starts, Flacco completed a career high 65.3 percent of his passes for 1,822 yards, six touchdowns and five interceptions.