Vikings coach Mike Zimmer said Friday that Case Keenum again will start Sunday against Baltimore with Sam Bradford being ruled out for the fifth time in the past six games. Bradford, who has a left knee injury, has not played or practiced since Oct. 9 at Chicago, when he was ineffective and removed in the final minute of the first half after aggravating his injury. When asked if he is certain Bradford will play again this season, Zimmer said, “I believe he will, yeah.” Also not practicing Friday was Nick Easton (calf), who is likely to be replaced at left guard for the second straight game by Jeremiah Sirles. Returning to practice were wide receivers Stefon Diggs (groin) and Michael Floyd (hamstring), with both likely to be listed as questionable for Sunday.