Mark Stone had an assist for his 400th NHL point. The Golden Knights captain leads them in scoring with 89 points (29 goals, 60 assists) in 93 games since being traded to Vegas from the Ottawa Senators on Feb. 25, 2019.
The Golden Knights canceled their postgame media availability due to NHL COVID-19 protocol.
The Ducks (5-6-3) lost in regulation for the first time in four games. Troy Terry, Adam Henrique, Ryan Getzlaf and Isac Lundestrom scored, and Ryan Miller made 26 saves for Anaheim.
Terry made it 4-2 at 5:02 of the third period, Henrique scored at 7:23 to make it 4-3, and Getzlaf tied it 4-4 on the power play at 9:59.
The comeback, I think, it shows our team's resiliency and that we can play with any team in this league," Terry said. "But there's no one that's happy right now. It's a mindset thing. It's been this way since I've been here, and I'm guilty of it. We can't be happy with coming back and making it close and playing Vegas to a close game."
Stephenson scored his third goal in two games at 10:56 of the first period, from Stone, to give the Golden Knights a 1-0 lead.
Marchessault made it 2-0 when Reilly Smith's pass deflected off his skate.