The team made the announcement minutes before warmups Thursday night, adding that Bergeron is day-to-day.
The 32-year-old forward showed no signs that he would be out of the lineup as he spoke with media earlier in the day in the Bruins' locker room. He has five assists through the first three games of Boston's first-round matchup against the Leafs, which the Bruins lead 2-1.
At Wednesday's off-day practice Nash took some line rushes alongside Marchand and Pastrnak, however coach Bruce Cassidy said Thursday when asked that it wasn't for any specific reason.
Bergeron was nominated as a finalist for the Selke Trophy on Thursday for the seventh season in a row. It's given annually to the forward who best excels in the defensive aspects of the game.