PITTSBURGH -- The Pittsburgh Penguins placed defenseman Brooks Orpik on the injured reserve Monday with a concussion.

Orpik was knocked unconscious by Boston's Shawn Thornton in the first period of a 3-2 Bruins' win on Saturday night. Orpik left the ice on a stretcher when Thornton grabbed Orpik from behind, threw him to the ice and punched him.

Penguins coach Dan Bylsma said Monday that Orpik was unconscious for "30 seconds or more."

Orpik flew home with the team, but is out indefinitely. Bylsma said Orpik is "doing quite well" but offered no timetable on a possible return.

Pittsburgh recalled defenseman Brian Dumoulin from Wilkes-Barre/Scranton of the American Hockey League to take Orpik's spot on the roster.