With a win, the Broncos can clinch a playoff spot if either the New York Jets or Pittsburgh Steelers lose Sunday.
It will be Osweiler's sixth consecutive start as Peyton Manning continues his rehab from a tear in the plantar fascia near his left heel he suffered in the Broncos' Nov. 8 loss in Indianapolis. Manning has not played since he was taken out in the third quarter of the Broncos' Nov. 15 loss to the Kansas City Chiefs.
"We're going with Brock; we'll rally around him,'' Kubiak said after Wednesday's practice.
Kubiak also outlined a different rehab schedule for Manning, who had returned to the practice field last week. Manning had thrown in Wednesday's and Thursday's practices last week but was then held out of Friday's practice because of what Kubiak called "soreness.''
Manning will go through morning workouts and not participate in practice.
"Brock is our starter moving forward and we're trying to get Peyton healthy,'' Kubiak said. "That's where we're at. The team knows that and if something were to change you'll be the second guys to know that, the team should always be first.''
Kubiak had said Monday that "nothing's changed" in the team's quarterback rotation, and Wednesday's announcement made it official. Kubiak has not formally named the starter the past two weeks until later in the week, but the fact Manning will not practice with the team this week means he has had a setback in his recovery.
"The most important thing is getting him healthy, and we took some steps last week toward doing that,'' Kubiak said. "A couple good steps and obviously Friday wasn't a good day compared to the others. ... Hopefully we'll have a good week this week and we'll see, just trying to get him healthy. ... He's doing things on the field all week; he's working in the morning. We've got some guys working with him, some cardio stuff going on with him ... that's what we've got going on this week.''
On the change in Manning's rehab schedule this week, Kubiak said, "He's working to get himself back, healthy to where he feels like he can go. I just think we were taking the steps we thought that were necessary last week and had a little hiccup along the way. We'll start the process again.''
Osweiler, who is 3-2 in his five previous starts, said any public uncertainty over who would play at quarterback has not affected him during his weekly preparation.
"It doesn't bother me either way,'' Osweiler said. "I'm going to prepare each and every week the same exact way. ... The delay on naming the starter doesn't bother me one bit.''
Osweiler has been treated this week for an injured left (nonthrowing) shoulder after a hit he took in Sunday's loss in Pittsburgh from Steelers linebacker Sean Spence on a 7-yard run in the second quarter. He was also headed to the doctor Wednesday because of an eye infection, but joked he could see well enough in practice "to hit the open receiver.''
Kubiak was also asked Monday whether there was a scenario in which the team could suit Manning up as the backup in a game if he were able to do more work in the coming weeks.
"Absolutely, absolutely, we're trying to work him back to where we feel like he can go play, he can go be himself. That's been the plan all along," Kubiak said. "We're not there yet, nothing has changed. ... [Manning] is doing everything we're asking him to do, and he's doing it because he wants to do it."
Osweiler will start for Broncos
Adam Caplan breaks down why the Broncos have decided to name Brock Osweiler the starting quarterback over Peyton Manning.