Vegas forward Jonathan Marchessault scored the first of his two goals 3:59 later to give the Golden Knights a 2-0 lead at the first intermission, a 180-degree reversal of fortune from Game 1 when Vegas trailed 3-1 after 20 minutes and never could find its way back into the game, which ended in a 4-2 loss.
"It was huge," Vegas defenseman Nate Schmidt said of the opening goal. "It just got (Tatar) into the flow of the game. Look at how many plays he made as the game goes on. He's comfortable. When guys are comfortable and confident, that is when they play their best."
Tatar, acquired in a trade from the Detroit Red Wings on Feb. 26 for three draft picks, including a first-round selection in the 2018 NHL Draft, played in place of David Perron, who was out with an illness.
Tatar did not want to be in the press box with the other scratches in Game 1, but he said he used the time wisely.
"You see how the play goes, which you can't see develop on the ice because it goes too fast," Tatar said. "But you see it from up top and try to learn from it and memorize it."
Vegas coach Gerard Gallant liked what he saw from Tatar.
"I thought he played great," Gallant said. "He played fast, he played quick and he was on top of the play. He was hungry to play. Again, he hasn't played a lot in the playoffs, but he is an important player for us when he gets the opportunity and that is what I want him to do."