Bergeron had been cleared for one-way contact -- he can hit, but can't be hit -- but he is 10 pounds lighter than his playing weight. He passed his neurological and psychological tests this week, but until he is full strength he can't get permission to play.
The 22-year-old Bergeron is expected to be re-examined in two weeks, Bruins spokesman Matt Chmura said, which would be in the middle of the first round of the playoffs. The Bruins entered Saturday's game against the Ottawa Senators in eighth place, two points ahead of Washington for the last playoff spot in the Eastern Conference.
Bergeron suffered a concussion when he was hit from behind by the Flyers' Randy Jones on Oct. 27. The NHL suspended Jones for two games, while Bergeron had missed 67 games entering Saturday's matchup against Ottawa.
The Associated Press contributed to this report.