ENGLEWOOD, Colo. (AP) Peyton Manning isn't giving Brock Osweiler any unsolicited advice this week as his longtime understudy prepares for his first NFL start.
''I'm not a coach, for one thing,'' Manning said. ''As I shared with him, he's probably going to have a lot of coaches this week - some who aren't coaches - that are going to be offering him tips of advice.''
So, Manning told Osweiler he'd be there for any questions he might have, ''but I'm not going to be one of those extra voices in his ear.''
More from FoxSports
Manning will be too busy trying to get healthy from a variety of injuries - foot, shoulder, ribs - that led to his playing the worst game of his career on the same day he became the league's all-time passing yards leader Sunday.
That prompted coach Gary Kubiak to make the switch with the Broncos (7-2) in a two-game slide heading into their game at Chicago (4-5).
Instead of making his 265th regular-season start Sunday, Manning will be in street clothes for the first time in his career, other than the season he missed following neck fusion surgery.
Osweiler will be making his first start since Dec. 22, 2011, when he threw for nearly 400 yards in Arizona State's 56-24 loss to Boise State in the MAACO Bowl.
''Peyton has been extremely supportive of me. He just said, `If you need anything throughout the week, I'm here for you. I support you 100 percent and go get a win in Chicago,''' Osweiler said.
Manning will spend all week with head athletic trainer Steve Antonopulos while the Broncos coaches put in a game plan for Osweiler, the fourth-year QB from Arizona State who turns 25 Sunday.
''I told Brock when I first walked in, `This is totally a blessing for you to be behind Peyton learning from him.' I think that it's a great opportunity for Brock to get in, play this game and show what he can do,'' said tight end Vernon Davis, whom the Broncos obtained in a trade from the 49ers earlier this month.
''I'm not worried. I'm not worried at all,'' Davis said. ''I think that he'll do a tremendous job leading this team, being a leader and taking over until Peyton is able to come back.''
Osweiler said he didn't expect many changes in the play calls, saying, ''we have one offense here.''
But two very different quarterbacks.
Instead of dialing down things for Osweiler's debut, Kubiak might actually be able to open up his playbook for the strong, mobile QB. The Broncos had to modify the system for Manning, putting their 39-year-old quarterback in the pistol or shotgun, which affected the run game and the play-action possibilities.
Osweiler has looked adept running the roll-outs, bootlegs and sprint-outs that might get more use this weekend.
Manning's play began to dip last season after he pulled a thigh muscle, so GM John Elway and Kubiak entered this season with a new plan to keep Manning fresh for the stretch run. They had Osweiler run the team every third day in training camp and then every Wednesday during the season.
While Manning hasn't been a big beneficiary of that, with injuries making the O-line a turnstile, Osweiler has taken advantage of his extra work with the starters, which showed Sunday when he led Denver on two late touchdown drives.
''He's grown from that,'' Kubiak said. ''He went in there and he played with a lot of confidence the other night.''
In some ways, Osweiler still has the mindset of a backup.
Asked what it was like when Kubiak announced in the team meeting Monday that he'd be starting, Osweiler said: ''First of all, it's very exciting, but at the same time, Peyton is still our guy. He's one of the best to ever do it. He's been extremely supportive of me since Day 1. He's taught me so many things, so I'm going to continue to support him.''
Nobody's sure when Manning will return to action, but Osweiler is only looking at this as a spot start.
''I'm the starter for this week at Chicago, but that's all it is,'' Osweiler said. ''We're focused this week, and then we'll reevaluate everything next week, but I stand by Peyton and support him 100 percent.''
And Manning stands behind Osweiler.
AP NFL website: www.pro32.ap.org and www.twitter.com/AP-NFL
Follow AP Pro Football Writer Arnie Melendrez Stapleton on Twitter: http://twitter.com/arniestapleton