Vanek was rotating with rookie Michael Bournival on right wing of a line with Brandon Prust and Daniel Briere, meaning there is a possibility Vanek will be scratched for Game 3 of the Eastern Conference Final in New York on Thursday (8 p.m. ET; NBCSN, CBC, RDS).
Vanek is tied for the Canadiens lead with five goals in the Stanley Cup Playoffs, but he has scored in three of his 13 games and failed to register a shot on goal three times, including the 3-1 loss in Game 2 on Monday.
Therrien would not confirm anything and for a second day in row refused to criticize Vanek's play.
"We're in the conference final," Therrien said. "To get here, we needed contributions from everyone. Every player who's played since the start of the playoffs has contributed in some way. That's important in my eyes."