The team announced that Manning was dealing with a thigh injury. He was also reportedly playing with flu-like symptoms.
Manning returned in the second half to help lead the Broncos to a 22-10 victory that clinched a fourth consecutive AFC West title. He finished with 233 yards and a touchdown and zero interceptions.
"I was in some discomfort and had some limitations, so obviously if you feel like you can't do your job and you can't move to protect yourself, you're going to hurt the team," Manning said Sunday, according to The Denver Post. "I felt I got a little relief there at halftime and was able to go the second half."
Over 14 games this season, Manning has completed 67.1 percent of his passes for 37 touchdowns and 11 interceptions. The 38-year-old is in his third season with the Broncos after spending his first 14 with the Indianapolis Colts.
The Broncos (11-3) face the Bengals in Cincinnati on Monday.