Thomas Vanek scored a hat trick and Ryan Miller  stopped 38 of 42 shots on the night as the Sabres handed the Bruins their first regulation loss of the season, 7-4, Thursday night at TD Garden. The Bruins were denied matching their best seven-game start in franchise history and fell to 5-1-1 on the season. Vanek now has 54 points in 46 career games against Boston.
The only significant action of the first period was a fight 2:53 into the game that had John Scott taking down Shawn Thornton  in stunningly fast fashion with several rights to the face and head of the Bruins enforcer. Both men served their fighting majors and then Thornton headed immediately down the Boston tunnel to the dressing room and did not return. The Bruins did not reveal the nature of the injury before announcing early in the second period that he would not return.
After a scoreless first period, the two teams combined for six goals in the second, with the division rivals splitting the difference for a 3-3 score after 40 minutes. The Sabres took the first lead of the game when Vanek one-timed a shot past Tuukka Rask  1:38 into the second.
The Bruins then answered with a dominating 10-minute stretch. Rich Peverley  scored his first on a Daniel Paille  rebound from the edge of the right circle at 5:12 to tie the game. Brad Marchand  then scored his fourth and fifth goals of the season just 3:11 apart, putting Boston up, 3-1 and capping a three-goal flurry in five minutes, 42 seconds.
But the game turned on two Bruins penalties called simultaneously as Milan Lucic  was whistled for boarding and Zdeno Chara  was called for holding, giving Buffalo a 5-on-3 power play for a full two minutes. The Bruins controlled the kill early but Vanek scored his second of the night and fifth of the season 60 seconds into the power play, making it 3-2. The Bruins killed off the final 60 seconds with Lucic still in the box. But the Sabres used the power play for valuable momentum, earning the equalizer when Tyler Ennis was left all alone on the right post in front of Rask. Vanek fed a perfect pass across the slot and Ennis didn’t miss.
The Bruins gained the lead again in the third when David Krejci  beat Ryan Miller  down low to the far post just 1:45 into the period. But the Sabres came back and took the lead on goals by Alexander Sulzer and Cody Hodgson.
The Bruins had a golden opportunity to tie the game by Miller made a big save on a slap shot from Chara with eight minutes left. Moments later, Tyler Myers took a four-minute high-sticking penalty when he clipped Paille. But that was weakened when Dennis Seidenberg  was called for tripping just 30 seconds into the man-advantage.
Vanek added insurance with his third goal of the night with 1:31 left for his eighth career hat trick and Jason Pominville added an empty-netter with 13.6 seconds left to cap off the scoring. The Bruins are off Friday before playing in Toronto Saturday night. For more from DJ Bean and Mike Petraglia at the Garden, visit the Bruins team page at weei.com/bruins .