Miller, a three-time Pro Bowler, has played with Manning in Denver since 2012.
"We can win a championship with Peyton. I think that's the only thing that matters," Miller said, according to the Post. "What else can I say? I think he's coming back. He said a long time ago that he would stop playing football when he felt like he was hurting a team more than helping a team. There's still so much he can do, so many wonderful things he can do for the Denver Broncos."
Manning said last week that he'd like to make a decision in the near future on whether he will be coming back.
The 38-year-old reportedly will not decide on a potential return until he undergoes a physical examination in early March.
Manning also said that new coach Gary Kubiak, team president Joe Ellis and general manager John Elway have instructed him to "take some time."
Manning, who will turn 39 in March, just completed his 17th season in the NFL and his third with the Broncos. He has two seasons remaining on the $96 million deal he signed with Denver in 2012.
The Broncos went 12-4 this season, finishing first in the AFC West before falling to the Indianapolis Colts in the divisional round of the playoffs.
Denver recently hired Kubiak to replace John Fox, with whom the team agreed to mutually part ways last month.