Lehner was the first goalie off the ice at Sunday's morning skate, typically an indicator of who will start that night's game. Sources told ESPN that Lehner and Marc-Andre Fleury were notified of the decision Saturday. Coach Peter DeBoer had declined to reveal a starter in a news conference on Sunday.
"I think I speak for all the guys on the team. We have confidence in both of them," defenseman Zach Whitecloud said.
Lehner had played just four times in the past 50 days. He was the Golden Knights' starter for all of last postseason but had been benched during the postseason as Vegas rode the hot hand of Fleury.
Lehner's only other playoff start this year was a disaster. The Golden Knights, coming off an emotional Game 7 win in the first round, left Lehner out to dry in a 7-1 loss to Colorado in Game 1 of the second round. Lehner allowed seven goals on 37 shots. Fleury returned to the net for Game 2 and every game since.
Fleury has been a leading Conn Smythe candidate throughout the playoffs. In 15 starts he is 9-6 with a .921 save percentage and 1.97 GAA.
However, he was coming off two straight losses. In Game 3, Vegas was leading 2-1 with less than two minutes remaining when Fleury made a costly mistake. He misplayed a puck behind the net -- leaving the net wide open for Josh Anderson to stuff in a game-tying goal.
Montreal won 3-2 in overtime and had a 2-1 semifinal series lead over heavily favored Vegas going into Game 4.
Teammates defended Fleury after Game 3. Captain Mark Stone called it "an unfortunate bounce."
In a Saturday news conference, Fleury laughed off the mistake and was ready to move on.
"It's part of the game, having to talk to you guys and being reminded of my screwups, right?" Fleury said with a laugh. "Obviously, I wish things were different. But it is what it is, and got to put it behind and get ready for our next game."
The Associated Press contributed to this report.