Ryan Callahan (knee) out 4-6 weeks

NEW YORK -- Already down one of their top defensemen, the New York Rangers were dealt another colossal blow in Tuesday night's 4-1 loss to the Nashville Predators.

Captain Ryan Callahan left the game with a Grade 2 MCL sprain. He is expected to miss four to six weeks.

Callahan sustained the injury while attempting to deliver a hit in the first period and did not return to the game. This makes the third injury that has sidelined the gritty winger so far this season.

Callahan, 28, missed the season opener with a shoulder injury -- he underwent surgery to repair a torn labrum over the summer -- and sat out seven games with a broken thumb suffered in mid-October.

"It's been a tough stretch for him, and we all feel for him," teammate Dan Girardi said. "Everyone has to step up a little more. He brings a lot to the team, a lot of different characteristics, and someone's going to have to find a way to step up for him."

The news could not have come at a worse time for the Rangers, as they dropped their third straight Tuesday night with an already-depleted lineup. Alternate captain Marc Staal left Saturday's 4-3 overtime loss to the New Jersey Devils with an injury that was confirmed Tuesday morning to be a concussion.

Callahan was considered a lock for the U.S. Olympic team that will compete in the 2014 Games in Sochi, Russia, and likely will be healthy in time to play. Callahan is in the last year of a three-year, $12.825 million deal.

With franchise goaltender Henrik Lundqvist now locked up long term -- he inked a seven-year, $59.5 million contract extension last week -- the Rangers were expected to turn their efforts toward re-signing Callahan soon.