Shawn Thornton

Bruins left wing Shawn Thornton looks to pass under pressure from Panthers right wing Krys Barch during a game last month in Boston. (Jared Wickerham / Getty Images / November 7, 2013)

Bruins enforcer Shawn Thornton has been suspended for 15 games by the NHL for punching and injuring Penguins defenseman Brooks Orpik on Dec. 7 in Boston, the longest suspension in the regular season handed down by Brendan Shanahan, the league's chief disciplinarian.

Orpik sustained a concussion from the first-period incident and is still dealing with lingering symptoms. Thornton could appeal the decision, which came down a day after his in-person hearing with the league. In the video explaining the decision, Shanahan described the incident and what led to the decision.

He spoke about how Thornton grabbed Orpik, kicked his feet out, and once Orpik was down on the ice, Thornton went on to throw two short punches.

"This cannot be described as a hockey play that went bad," Shanahan said in the video. "Nor do we consider this a spontaneous reaction to an incident that just occurred.

"Rather, it is our view that this is an act of retribution for an incident that occurred earlier in the game. The result of this action by Thornton was a serious injury to Orpik."

Thornton had never been fined or suspended in his 11-year NHL career. He already has missed three games since the incident and apologized for his actions in postgame interviews.

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