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."
Vanek had been playing on a line with Alex Galchenyuk and Tomas Plekanec, but his spot on was filled by captain Brian Gionta. Plekanec and Gionta spent most of the season playing together, and Therrien admitted he is trying to light a spark on his second line.
Asked what he likes about the Plekanec-Gionta combination, Therrien essentially confirmed they will be playing together in Game 3.
"One thing, the Plekanec line needs to give us more," Therrien said. "I'm ready to stick sometimes with combinations and with three guys working together as long as I see that even if the results sometimes aren't there, but the chances are there. But if I see there are no chances, not much happening, now I'm at a point where I have to make some decisions, and those are the reasons why at times a coach will make decisions regarding lines.
"[People] normally judge with goals and assists. That's not always the way we do things, but if I see they've got chances, I like to stick with it. If I see it's the opposite, OK, now I've got to take some decisions. Hopefully, by making some changes, something's going to happen."
Moving Gionta up with Plekanec breaks up what has been a very effective third line for the Canadiens with Lars Eller and Rene Bourque. Gionta's spot on right wing of that line was taken by Dale Weise at practice Wednesday, with Vanek and Bournival taking turns playing in Weise's spot on the fourth line with Briere and Prust.
Vanek played with Briere with the Buffalo Sabres in 2006-07, and when asked if that chemistry would be something Therrien would try to rekindle, he dismissed it as being ancient history.
"You know what, the past is the past, you know?" Therrien said. "I know they've had good results a few years ago, but it's a long time ago. So yes, they've built chemistry in the past, but don't read too much into it."
Vanek's struggles became a talking point at practice, but the Canadiens players were standing behind the scorer who was acquired by general manager Marc Bergevin prior to the NHL Trade Deadline from the New York Islanders.
Vanek had his most success playing on a line with David Desharnais and Max Pacioretty, but those two combined with Brendan Gallagher had a tremendous Game 2 and were the only Canadiens forwards who found their line still intact at practice.
"He's contributed to this team's success in the playoffs. He knows it," Pacioretty said of Vanek. "We all talk. Behind closed doors … we all want to help this team win, and we all like where we stand right now with the team. He's fine. He's going to be fine."
Therrien denied Vanek is injured when he was asked Tuesday, but the possibility does exist he has a lingering injury that is hampering his ability to shoot.
In Game 3 of the second-round series against the Boston Bruins, Vanek went to the dressing room when he was injured after a body check by Canadiens defenseman P.K. Subban on Bruins forward Reilly Smith. As Subban bounced off Smith on a hit he was penalized for, he hit Vanek. Vanek returned to the game, but his numbers have dropped.
In the six games since, Vanek has seven shots on goal, scoring twice, on a tip in and what was essentially an empty-net goal but was credited as an even-strength goal because Bruins goaltender Tuukka Rask had not reached the bench.
Vanek has attempted to shoot 15 times in those six games. In the six games prior to Game 3 against Boston, Vanek had 14 shots on goal.
If Vanek is nursing an injury, sitting him out of Game 3 would give him five days of rest between Game 2 on Monday and Game 4 on Sunday.
If, on the other hand, Vanek does play on the fourth line Thursday, Pacioretty sees it as a benefit to the Canadiens' scoring balance.
"It's nice to have huge numbers in the playoffs, but you look at the teams that are rolling right now, it's the teams that have balanced scoring and everyone contributing," he said. "I don't know what's going to happen, but it's nice to have four lines that you can trust at any moment."