Jeff Skinner, Tage Thompson and Lawrence Pilut scored to help Buffalo get its first win at Vegas after coming in 0-3-1 all-time. The Sabres improved to 6-2-1 in December, after going 4-9-1 the previous month, and moved into a fourth-place tie with Florida in the Atlantic Division with 34 points.
Chandler Stephenson and Reilly Smith scored for Vegas, while Adin Hill made 15 saves. The Golden Knights dropped to 8-9-1 at home. The Golden Knights have been outscored 26-11 in their last seven home games - including six losses.
After a rather pedestrian first period that was filled with heavy hits and heated exchanges, the Sabres got a spirited pep talk from captain Kyle Okposo that reverberated throughout the locker room.
''We had our captain come in and challenge us. He's an unbelievable captain, unbelievable character, unbelievable player and you know what, when he says something, everyone's listening,'' former Golden Knight Alex Tuch said. ''I thought we stepped up to the occasion and we responded well.''
Early in the second, Tuch skated into the zone with linemate Thompson strategically trailing to draw the coverage. Tuch sent a pass to the left lane for Skinner, who fired it past Hill to give Buffalo a 1-0 lead at 1:53.
The Sabres extended the lead to two goals when Thompson took Casey Fitzgerald's pass to the circle after a Vegas turnover, dangled around sliding Golden Knights defenseman Nic Hague and had the patience to wait for Vegas' Phil Kessel to skate by before lasering a shot by Hill at 7:15.
Pilut increased the lead to 3-0 with 6 1/2 minutes left in the second when the Sabres won a faceoff and he took Okposo's pass at the point and ripped a slap shot from just inside the blue line.
Meanwhile, Luukkonen remained brilliant, including a stuff on Vegas captain Mark Stone's breakaway.
Stephenson finally got Vegas on the board when he took a feed from Michael Amadio, raced in untouched on a breakaway and ignited the crowd with the team's first goal of the game at 3:54 of the third.
Then it was Luukkonen's turn again, as he stretched across to make a save on Smith at the backdoor during a penalty kill, one of five saves during Vegas' power-play opportunity.
Jonathan Marchessault also had a prime opportunity with a penalty shot with 6:57 left, but as he did all night, Luukkonen showed composure in making a huge save.
''It's always good as a goalie when you can make a play like that, which kind of might change the direction of the game at that point,'' Luukkonen said.
Smith made it a one-goal game late in the third by beating Luukkonen through traffic with 2:21 remaining.
Yet despite Vegas outshooting Buffalo 23-5 in the third period, it wouldn't dim Buffalo's star of the night, Luukkonen.
''Just one of those nights where it's not going in and I thought we battled hard we created a lot of good locks in the third period,'' Smith said. ''Just wasn't our night.''
NOTES: Stephenson's goal extended his point streak to five games (two goals, six assists). ... The Golden Knights finished 0 for 3 on the power play, failing to score with a man advantage for the first time in five games. ... Buffalo came in with the second-best power play in the league, but finished 0 for 1 with an extra skater.
Sabres: Host Tampa Bay on Friday night.
Golden Knights: Host Arizona on Wednesday night.
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