Penguins defensemen Kris Letang and Zbynek Michalek are out indefinitely because of concussions that were diagnosed over the weekend.
The two were injured Nov. 26 late in a game at Montreal and missed their fourth game Monday when the Penguins played the Boston Bruins at Consol Energy Center. Although they each passed an ImPACT neurocognitive test, concerns remained.
They will remain out until they are symptom-free and get medical clearance.
Letang, who also has a broken nose, got leveled by Montreal's Max Pacioretty , who received a three-game suspension. Going into games Monday, Letang ranked among the top-scoring NHL defensemen with 19 points.
Letang apparently had a delayed onset of symptoms. Penguins coach Dan Bylsma defended the decision that allowed Letang to return the night he got hurt and score the winner in a 4-3 overtime game, saying Letang was cleared by Canadiens team physician David Mulder .
"He's well-respected," Bylsma said of Mulder. "He went and saw Kris, and Kris, at that time, didn't have any issues other than they rearranged his nose. He was fine and ready to go back on the ice.
"Dr. Mulder went through the series of steps to clear him to go back in."
It's unclear how Michalek got hurt. He has a goal and three assists in 14 games after earlier missing 10 games because of a broken finger.
The Penguins promoted defenseman Alexandre Picard from Wilkes-Barre/Scranton of the American Hockey League. He played in his eighth NHL game of the season in his third recall. Already in the lineup were rookies and recent call-ups Robert Bortuzzo and Simon Despres .
Injuries in the third period of a 3-2 win Saturday at Carolina also kept defenseman Deryk Engelland and forward Richard Park out of the Boston game.
Engelland has an unspecified injury. Bylsma described him as day-to-day.
Park appeared to favor his right leg after blocking a shot in the final seconds of regulation during a furious stretch when the Penguins were short-handed. Bylsma did not divulge Park's injury but said after the game-day skate that Park was a game-time decision, an indication the injury might be minor. He was replaced in the lineup by Joe Vitale .
Defensemen Ben Lovejoy (broken wrist) and Brian Strait (hyperextended elbow) and forward Dustin Jeffrey (knee surgery) have not returned to practice.
Center Jordan Staal , meanwhile, played against the Bruins after adding a visor to his helmet. He got cut on the left cheekbone Saturday by a puck.
The game against the Bruins was center Sidney Crosby 's eighth since he missed 61 games because of a concussion.
Saturday, St. Louis winger David Perron returned after missing 97 games over 13 months with the same injury. As with Crosby in his first game back, Perron scored his team's first goal.
"You can relate to things that he's gone through," Crosby said. "You can relate to all the things that come with it.
"You're happy to see a guy come back and be healthy and play a game he loves to play. That was really nice to see. Hopefully, things will continue to go well for him."
The Blues fetched the puck from Perron's goal as a keepsake. Crosby got a different souvenir from his first goal.
"I have my stick," Crosby said. "But just being back is enough."
Among the 29 players who made the preliminary roster for the United States national junior team are forward Kenny Agostino , a Penguins fifth-round draft pick in 2010, forward Josh Archibald , a Penguins fifth-rounder this year, and four locals: goaltender John Gibson and forwards J.T. Miller , Brandon Saad and Stephen Johns .
They are invited to a camp in Alberta beginning Dec. 17. The final 22-man squad is expected to be named Dec. 22.
For much more on the Penguins, read the Pens Plus blog with Dave Molinari and Shelly Anderson at www.post-gazette.com/plus . Shelly Anderson: email@example.com , 412-263-1721 and Twitter @pgshelly.