Crosby, who leads the NHL with 32 goals and 66 points, missed the Penguins' 2-1 shootout loss in Montreal on Thursday night. He flew back to Pittsburgh to be re-evaluated by team doctors, who updated coach Dan Bylsma about the extent of Crosby's injury following the game.
Crosby had played each of Pittsburgh's first 41 games this season after he missed just one last season, when he tied for the league lead with 51 goals.
"We play 40 minutes a game without Sid on the ice so we're comfortable with knowing how we need to play and how it's going to be," Bylsma said. "We're going to keep playing exactly that same way and figuring out ways to win hockey games."
The injury reportedly occurred Wednesday night in an 8-1 home win over Tampa Bay, possibly on a hit by Lightning defenseman Victor Hedman. Crosby had one assist in the win, his first point in three games following a 25-game point streak.
"You don't want to see a guy go down like this, especially him, but we have to regroup and play better. That's it," Penguins defenseman Kris Letang said.
Crosby absorbed a blindside hit from Washington's Dave Steckel in the Winter Classic on Saturday.
"We wouldn't have thought he was OK to play," Bylsma said following the loss in Montreal when asked if Crosby displayed any symptoms before Wednesday night's game. "He certainly saw doctors."
The Penguins were also without forward Matt Cooke in Montreal. Cooke returned to Pittsburgh because of personal reasons.