Mathis returns to practice

INDIANAPOLIS -- Indianapolis Colts defensive end Robert Mathis practiced Friday for the first time this week and is listed as questionable for Sunday's game against the Denver Broncos.

A Pro Bowl selection last year, Mathis missed practice Wednesday and Thursday with a quadriceps injury.

Right tackle Ryan Diem is also questionable after missing his second straight day of practice with a hamstring injury. Left tackle Charlie Johnson returned to practice after missing last week's game with a foot injury and is listed as questionable.

Four players have been ruled out of the game: running back Donald Brown (chest), safety Aaron Francisco (ankle), receiver Anthony Gonzalez (knee) and kicker Adam Vinatieri (knee).