The Ducks scored 18 seconds apart in the second period to take a 2-1 lead, but Vegas scored 31 seconds apart, also in the second period, to move back ahead 3-2.
"We scored a couple goals and we get everything going our way," Ducks coach Randy Carlyle said. "We're feeling pretty good about ourselves and then we start turning the puck over."
Nosek tied the score 2-2 at 10:15.
The puck came out to Vegas defenseman Brayden McNabb along the wall and he sent it toward the Anaheim net. Gibson made the save, but the puck popped in the air and landed next to him in the crease. Nosek spotted it first and pushed it across the goal line with one hand on his stick.
Pacioretty gave the Golden Knights a 3-2 lead at 10:46 in his first game after missing seven with a lower-body injury.
The Ducks lost possession at the Vegas blue line and Alex Tuch passed the puck ahead to Paul Stastny coming through the neutral zone. Stastny kept possession until he got to the right face-off dot and then slid it to Pacioretty, who shot into an open net.
"He made that an easy lay-up for me," Pacioretty said.
The Golden Knights were on their power play for 4 1/2 consecutive minutes in the third period, including 90 seconds with a 5-on-3, but could not add to their lead.
Vegas was on a delayed penalty when Schmidt scored on a point shot through traffic for a 1-0 lead at 6:52 of the first period.
The Ducks nearly tied the score when a centering pass went off Ducks forward Brian Gibbons as he battled for position in front of the net. The puck hit the cross bar and came down on the goal line, but Vegas defenseman Deryk Engelland was able to sweep it away.
"The first period was one where we watched them do the things that they're very good at, and we really didn't get involved in the game physically," Carlyle said. "For whatever reason, they were quicker, faster, executed at a higher level than us."
The Ducks went on their first power play at 1:22 of the second period, and Sprong scored on a wrist shot from above the right circle to tie it 1-1 at 1:57.
Rowney finished off a feed from defenseman Hampus Lindholm for a 2-1 lead at 2:15.
"They came out the shift after [Rowney's goal] and really pushed us back," Lindholm said. "We need to feed our energy when we score goals, keep going. One-goal hockey game in this league doesn't matter much, especially when you have that much hockey left to play."
