Minnesota Vikings tight end John Carlson sprained his knee in practice on Tuesday, and it could keep Carlson out of action for several weeks, 1500ESPN.com reported. The preliminary diagnosis is a sprained medial collateral ligament, but Carlson was scheduled to have an MRI performed to pinpoint the problem. "If that (sprained MLC) is what it turns out to be, you don't have to have any surgery," Frazier told 1500ESPN.com. "It heals by itself. So, it's a little bit more of a pain tolerance thing, depending on how he feels." Fraizer also said the injury might sideline Carlson for a while, although it was too soon to make an educated guess how long he would be out. Carlson, 28, signed a five-year, $25 million contract with the Vikings in March. He sat out last season in Seattle with a shoulder injury, but he caught 136 passes over his previous three seasons with the Seahawks.