The center was scratched with an upper-body injury.
The Bruins lead the best-of-7 series 3-1. Bergeron is day to day with Game 5 on Saturday at Boston (8 p.m. ET; NBC, CBC, SN, TVAS).
"He had an upper-body injury we were managing and he wasn't able to go," Boston coach Bruce Cassidy said. "... Hopefully he's better and ready to go Saturday."
RELATED: [Complete Bruins vs. Maple Leafs series coverage]
Bergeron combined with linemates Brad Marchand and David Pastrnak for 20 points (five goals, 15 assists) in the first two games, won by the Bruins. The line did not have any points in a 4-2 Game 3 loss Monday, when Bergeron played 21:44.
Marchand scored and Pastrnak had two assists Thursday with Riley Nash taking Bergeron's spot on the top line, as he did during the regular season when Bergeron was injured.
Bergeron is a finalist for the Selke Trophy, given to the player voted to be the best defensive forward in the NHL.
