The Vikings now have four quarterbacks on the 53-man roster, but Kyle Sloter, who was inactive for the last eight regular-season games, definitely will be inactive again Sunday.
Bradford's activation does not guarantee he will be among the 46 active players Sunday, and it's unclear whether Bridgewater will continue to back up Keenum as he has been doing since Week 10 or whether the Vikings will turn to Bradford now that he is back on the active roster.
The Vikings haven't dressed three quarterbacks for a game since November 7, 2013, when Leslie Frazier was the coach and Christian Ponder, Matt Cassel and Josh Freeman all were active against Washington. He returned to practice last week, but coach Mike Zimmer said Friday he hadn't made a decision about whether to add Bradford to the active roster, while refuting a Boston Globe report that the Vikings would bring Bradford back.
Theismann has no inside knowledge on who might serve as Keenum's backup.
Bradford, who was placed on IR on November 8 with a left knee injury, returned to practice last week and completed his fifth practice Friday.
Bradford, Bridgewater and Case Keenum are all scheduled to become free agents after the season, and Bradford's return to health during the playoffs could help his case if he hits the open market in March.
Bradford aggravated his knee against the Bears and was ineffective before being replaced late in the first half by Keenum, who has started every game since.
Bradford has participated in five practices since returning January 2. In 15 games played, he posted career highs across the board with 3,547 yards with 22 touchdowns with just seven interceptions while holding a 98.3 quarterback rating. There's not anything noticeable there.