MANKATO -- The Vikings' tight end-friendly offense will have to make due without John Carlson for at least two weeks.

A magnetic resonance imaging (MRI) test performed Tuesday night confirmed the initial diagnosis of a sprained right knee. It's a Grade 2 sprain to the medial collateral ligament, which coach Leslie Frazier said will take "maybe a week or two" to heal well enough for Carlson to return to the field.

"A lot of it will depend on his pain tolerance," Frazier said. "Hopefully, in the next week or two, two weeks at the most, we'll have him back."

That's both good news in that it's not a more serious injury requiring surgery and bad news in that offensive coordinator Bill Musgrave has designed a ball-control, multiple-tight-end offense that runs the ball and moves the first-down marker with high-efficiency throws to the tight ends. The position is so highly regarded that the Vikings targeted Carlson as their premier offseason free-agent aquisition, luring him from his visit to Kansas City with a five-year, $25 million contract.

"You lose that veteran presence on the field, although he'll still be in meetings," Frazier said of Carlson. "And the fact that it's a new offense for him. The terminology. Not just hearing it in the meetings, but being able to go out and practice his movements, that part of it. But he's a pro. He'll pay attention and when he comes back, he'll be ready to go."

It's a setback for the offense, for sure. But it's happening so early in camp that it's far from insurmountable. In fact, in some ways, it will help develop rookie Rhett Ellison, Mickey Shuler and Allen Reisner, the surprise of last year's training camp as an undrafted rookie.

"It will probably increase their snaps, which is not a bad thing," Frazier said. "We'd like to see Mickey Shuler, see how he does. We'd like to see Allen Reisner, see how he does, as well as Rhett. And Kyle [Rudolph], we want to make sure he continues to progress in his second training camp."

Carlson injured the drill during an portion of practice when the team was going 11 on 11 and tackling running backs to the ground. It was the first time they tackled in camp this summer. (But, hey, these fellas have to go full-go at some point, right?)

"Whether we were in pads or not, I don't know that it really would have mattered," Frazier said. "He was blocking someone and another guy fell on the back of his legs. That tends to happen sometimes during drills. Legs get caught up and guys trip and fall."