Case Keenum will make his fifth start of the season in the absence of Bradford, who aggravated a knee injury in Week 5 against the Bears.
Vikings coach Mike Zimmer said he still believes Bradford will return at some point this season.
"I believe he will, yeah," said Zimmer, who added that Bradford saw a specialist last week.
Diggs also was injured in Week 5, suffering a groin injury, and has not played since.
Left guard Nick Easton, who suffered a calf injury against the Bears, also will miss a second straight game. And left tackle Riley Reiff, who was not on the injury report Wednesday or Thursday, was limited during Friday's practice with an ankle injury and is listed as questionable for Sunday's game.
The Vikings, who are tied atop the NFC North standings with Green Bay at 4-2, host the Baltimore Ravens on Sunday.
ESPN's Courtney Cronin contributed to this report.