A concussion is at the root of Boston Bruins defenseman Charlie McAvoy's absence, general manager Don Sweeney announced Friday.

The 20-year-old has missed the Bruins' last eight games, having not suited up since Oct. 18 against the Edmonton Oilers when he suffered the head injury.

"He’s been in protocol since (the Edmonton game) and is progressing - no timeline (on a return) but making progress," Sweeney said.

Sweeney noted that the Bruins aren't sure when exactly the hit that gave McAvoy the concussion occurred, but the blue-liner did skate in the last few days, according to Joe Haggerty of NBC Sports Boston.

Injuries have limited the sophomore to just seven games this season, but he's been productive when healthy, contributing one goal and six points.

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