Reilly Smith and Jonathan Marchessault scored, and Marc-Andre Fleury made 24 saves for the Golden Knights, who lost for the first time with a chance to win a Stanley Cup Playoff series; they were 3-0 in their inaugural season in 2017-18.
"It was a game that could have gone either way, and they made just a couple more plays on their goals," Vegas forward Max Pacioretty said. "They played a strong game, we knew that they would play their best. We have a little bit better we feel to give in this next game and hopefully win a hockey game. So we forget about it and move on to the next one."
Hertl gave the Sharks a 1-0 lead 1:16 into the first period on their first shot of the game, a wrist shot from the left face-off circle.
"We talk about start, and we started great today," Hertl said. "We get the lead, first goal, and right away, second goal. It's better play if you don't have to chase the game from the first minute."
Logan Couture made it 2-0 at 11:00, scoring on the rebound of a shot by Timo Meier.