Carlson's immediate availability is uncertain. (AP)

Former Seahawks tight end John Carlson missed the 2011 season with a shoulder injury but that didn't prevent the Vikings from signing him to a five-year, $25 million deal this spring. At the time, the move was a surprise not only because Carlson had struggled to stay healthy, but also because Minnesota, a team with myriad needs after a three-win effort in 2011, used a second-round pick on tight end Kyle Rudolph 11 months before.

That said, with a lot invested in young franchise quarterback Christian Ponder and a dearth of playmakers outside of Adrian Peterson (who's also returning from injury) -- not to mention the NFL-wide move to multiple tight end sets -- it's easy to see why the Vikings had interest in Carlson.

But as they say, the best laid plans …

Carlson suffered a sprained MCL during Tuesday's practice. That's the initial diagnosis according to coach Leslie Frazier by way of's Tom Pelissero.

"If that's what it turns out to be, you don't have to have any surgery," Frazier said. "It heals by itself. So, it's a little bit more of a pain tolerance thing, depending on how he feels."

Carlson will have an MRI Tuesday. Beyond that, his future -- at least in the near term -- remains undecided. Frazier was asked if Carlson's knee could keep him out of action for a while.

"It could. It could," he said. "We'll see. They'll tell me more when we get back in. But initially, that's what they told me -- sprained MCL."

Earlier this week, Carlson wasn't quite ready to call the Vikes' tight end situation all that similar to that of the Patriots, who feature Rob Gronkowski and Aaron Hernandez. "To compare us to those two tight ends is not something I'm going to do right now," he said according to Pioneer Press. "We've got a lot of work to do; we have a long ways to go. It's been done. It's being done out there. We have to work to improve to get toward that point."

Rudolph added: "If we can take both of those aspects of their game and implement it to what we're doing here, we have a chance to be successful."

That scenario now depends on the results of Carlson's MRI and any recovery time he'll need before again seeing the field.

Carlson had his best season as a rookie in 2008 when he caught 55 passes for 627 yards and five touchdowns. Rudolph, meanwhile, hauled in 26 receptions last season for 246 yards and three touchdowns.

For more NFL news, rumors and analysis, follow @EyeOnNFL on Twitter, like us on Facebook, and subscribe to our Pick-6 Podcast and NFL newsletter. You can follow Ryan Wilson on Twitter here: @ryanwilson_07.