Freeman was hurt late in last week's loss to Tennessee and was limited in practice on Thursday and Friday. He had a string of 36 straight starts stopped.
The Bucs made a roster move on Saturday in anticipation of Freeman's status, promoting quarterback Rudy Carpenter to the active roster. He had been on the practice squad all season after serving as the Bucs' third quarterback last year.
Freeman has thrown for 2,715 yards with 12 touchdowns and 16 interceptions this season. Johnson has completed just 2-of-7 passes for 14 yards in mop up duty this year.