Per Chad Graff of the Pioneer Press, Vikings head coach Mike Zimmer noted Bradford is "feeling better, he's just not ready to play" when he announced the quarterback wouldn't play Sunday.
Bradford hasn't played since Week 1 against the New Orleans Saints when he threw for 346 yards and three touchdowns in Minnesota's 29-19 victory.
ESPN's Chris Mortensen reported on Sept. 15 the Vikings had "some concerns" about Bradford's knee after he had "swelling, pain and discomfort" after the Saints game that required an MRI.
Zimmer has been avoiding specifics about Bradford's potential return timetable, saying after a Week 2 game against the Pittsburgh Steelers his quarterback could play "one week from now" or "six weeks from now" but that he's "fine."
The Vikings will turn to Case Keenum for the third straight game. He was terrific in Week 3 against the Tampa Bay Buccaneers with 369 yards and three touchdowns in a 34-17 win.