Ivan Barbashev extended the lead to 3-0 at 1:20 of the second period. He received a stretch pass from Brayden McNabb and roofed a shot over Grubauer's glove on a breakaway.
McCann got Seattle to within 3-1 at 8:19. He scored over Hill's left shoulder from the low slot after Jordan Eberle's pass, which was intended for Justin Schultz, deflected to him off the skate of Marchessault.
Jack Eichel scored an empty-net goal at 18:45 of the third period for the 4-1 final.
The win capped off a whirlwind few days for Vegas, which received its championship rings on Sunday and was on hand for "Monday Night Football" between the Las Vegas Raiders and Green Bay Packers.
“We had a lot of things going on in your life, and try to enjoy what we accomplished and prepare for a season. So you try to balance both,” Eichel said. “It’s an amazing experience to watch a banner go up. You want to enjoy every moment.”
NOTES: Tanev left the game at 6:02 of the third period after being hit by Howden, who was assessed a match penalty for an illegal check to the head on the play. Hakstol did not have an update postgame. ... Golden Knights forward William Carrier left at 7:09 of the second period with an upper-body injury. “When you don’t come back, that usually means it’s a little more serious than a little nick,” Cassidy said. “He’ll get looked at tonight or at the latest tomorrow morning. Hopefully it’s nothing long term.” ... Vegas has won five straight season openers, the longest active streak in the NHL.