Broncos quarterback Peyton Manning is back at practice. As a backup to Brock Osweiler.

For the first time in his NFL career, Manning enters a week as No. 2 on the depth chart as the Broncos seek their fifth consecutive AFC West title.

Manning, 39, accepted the role, even if he never has filled it before.

“It was a positive step to be back on the field and maybe make more of a contribution during the week of practice and on Sunday than just being in street clothes,” Manning said Wednesday. “I’ll do what I can do to help the team, help Brock. All the credit goes to Brock (on how he has played). That’s where the credit belongs. I will be there to help and support him in anyway I can.”

Kubiak eliminated any quarterback controversy by declaring Monday night that “nothing has changed” with Osweiler’s status.

This represented a different tactic from the previous two weeks, when the Broncos’ coach waited until Wednesday to reveal his plans for the position. Kubiak praised Manning’s handling of the decision.

“His confidence is up, and where he’s at mentally and physically, it’s time to take the next step,” Kubiak said. “I like the way he has battled to get to this point. He’s a competitor. Everyone wants to play. But he also understands where we are at and he wants to do what’s best for the team, and I am proud of him for that.”

Manning spoke humbly of the situation Wednesday, bristling only briefly when asked about his conversations with Kubiak throughout his recovery.

“He seems to share everything that we discuss. I don’t have any more to add to what he said about it,” Manning said.

Manning’s demotion marks the latest chapter in a turbulent year. He entered the season with a chance to become the all-time winningest quarterback. Manning will finish the year tied with Brett Favre at 186 regular-season victories. Manning hasn’t entered a game as a backup since his 1994 freshman season at the University of Tennessee when he sat behind Jerry Colquitt and Todd Helton on the depth chart.

“I anticipate preparing like I always have, studying on my own, being in meetings, that’s the only way,” Manning said.

Proving the torn plantar fascia in his left foot can withstand team practice is Manning’s next step. He failed to make it through three consecutive practices leading up to the Pittsburgh Steelers game on Dec. 20. Manning hasn’t practiced a full week with the team since late October, and despite not playing since Nov. 15 he has thrown 17 interceptions, worst in the NFL.

Osweiler has a 4-2 record as a starter, including Monday’s victory over Cincinnati which clinched a playoff berth.

“Brock has done a (heck) of a job,” Kubiak said. “I think it’s a great thing, Peyton being healthy and being available for this football team. Let’s take this next step. But Brock is our quarterback.”

With a victory over the Chargers, the Broncos would earn a postseason bye. A loss coupled with a Kansas City Chiefs victory would cost the Broncos the division crown and force a road game in the first round of the playoffs.

Manning declined to address whether he believes he can win the starting job back.

“I haven’t thought about that. I want to get through this week at full capacity. I want to do whatever I can to help us get a win Sunday,” Manning said. “It’s a big game with a lot on the line.”

Troy E. Renck: trenck@denverpost.com or @troyrenck