The Vikings’ top three quarterbacks all are scheduled to become free agents March 14. Minnesota chose not to franchise Case Keenum and now risks losing all three. “I would like to keep all three of them,” Vikings coach Mike Zimmer said. “These kids have busted their rear ends for me however number of years — some of them four; some of them two; some of them one. They know how we do things now. I think that’s important for the culture of this franchise, the culture of this organization. Again, it’s going to come down to financial things, financial for them, and maybe some of them don’t get to free agency. We’ve still got some time. I know there’s a lot of rumors, a lot of different things going on out there. But don’t believe everything you hear unless it’s from me.” Keenum, Sam Bradford and Teddy Bridgewater all have questions. Bradford played only two games last season because of knee injury Zimmer characterized as “degenerative.” Bridgewater spent 14 months rehabbing from a dislocated left knee, missing the 2016 season and playing only nine snaps last season. Keenum was a journeyman quarterback, playing for three teams in his first five seasons, before going 11-3 with the Vikings in 2017.