Denver Broncos right guard Chris Kuper broke his left forearm at practice Tuesday and could miss up to six weeks.
Kuper got caught at the bottom of a pile during team drills early in practice and retreated to the team's Dove Valley headquarters for X-rays.
The Broncos said they expect Kuper to fully recover in four to six weeks.
He'll be replaced by Manny Ramirez, a sixth-year pro who started at right guard in the team's preseason opener at Chicago last week.
The stalwart of an otherwise young offensive line, Kuper was making progress in his return from a broken left leg in last season's regular season finale when he got hurt again.