OTTAWA -- After just his third start and fourth NHL appearance, Maxime Lagace sounded like he'd be waiting forever to raise his arms after a game.

"It's good to get that first one, finally," Lagace said after making 24 saves in Vegas Golden Knights' 5-4 victory over the Ottawa Senators at Canadian Tire Centre on Saturday afternoon.

"The guys played really well. I have them to thank for that win. On to the next one."

The Golden Knights led by a pair of goals when Senators captain Erik Karlsson made things interesting with 34 seconds left. Another Ottawa push resulted in a Derick Brassard deflection grazing the side of the post.

"I got nervous a little bit, but not nervous to the point where it could have affected my game," Lagace said. "I think they came back right away with a tip and I got just a little piece of it. That scared me a little bit, but we got it, so it's all good."

Erik Haula scored twice and added an assist to lead the Knights. Jonathan Marchessault had a goal and two assists, while William Karlsson and Alex Tuch also had goals.

The Golden Knights scored three power-play goals on five opportunities. They had another three seconds after a Senators penalty had expired.

"Just work ethic and we finally got some bounces, especially our unit," Haula said on the secret to the power play's success. "We've been struggling a little bit. We just simplified a little bit and said we just got to go to work. If you're slumping a bit or whatever it is, the simpler the better. Give it a chance."

Senators coach Guy Boucher said his team's penalty killing problems cost them the game.

"We beat them 3-1, 5-on-5," said Boucher, who also gave Vegas full marks. It's exactly what we were expecting. It's the hardest working team we've seen up to now. It's hard to get through them."

Mark Stone, Ryan Dzingel and Alex Burrows had the other Ottawa goals. Craig Anderson made 29 saves while giving up too many second chances.

"We wanted to attack Anderson from down low," Tuch said. "That's what we did. We noticed he wasn't handling rebounds that well early on and there were a couple of rebound goals on the power play. We got some good net presence in front and were able to get pucks right at the side of the net for the rebounds."

The win ended a three-game losing streak for the Golden Knights (9-4-0). The Senators (6-3-5) have just one win in their last four.

"This was probably not a game we played up to our capacity," said Karlsson, admitting the Golden Knights had more "energy" than the Senators. "Games like this happen. We have to find a way around that. Unfortunately, today was not one of those days."

The Golden Knights opened the scoring for just the sixth time in 14 games. Three times the Senators came back, until William Karlsson's wraparound gave Vegas its first two-goal lead at 3:29 of the third.

"They clog the middle really well," Dzingel said. "If you try to make plays through the middle that's where they hurt you. They transition really fast. In this league it's hard to catch up."

The Senators lost Zack Smith to an undisclosed injury when he was hit by Colin Miller in the third. Boucher said he didn't know if Smith would make the trip to Sweden, where the Senators are now headed for back to back games against the Colorado Avalanche on Friday and Saturday.

Golden Knights coach Gerard Gallant was happy for Lagace, the fourth goalie he's had to use already this season because of injuries.

"It was great for him," said Gallant. "He played a real strong game tonight. They made it closer at the end than it should have been, but we still got the two points. We played great for 50 minutes. I liked the way our team played for most of the night.

All our guys worked really hard for 50 minutes and then I think we thought we won the game and they let off a little bit. We've got to make sure we complete those games harder at the end."

NOTES: Senators LW Alex Burrows picked up the 400th point of his career. ... The Senators recalled D Ben Harpur on Friday then made him a scratch along with D Mark Borowiecki, who is just getting over a viral infection that has caused him to miss three games ... Golden Knights scratches were D Jon Merrill, D Brad Hunt and LW Brendan Leipsic ... Vegas continues its six-game road trip with stop No. 5 Monday in Toronto to face the Maple Leafs.