The NHL suspended Byfuglien for four games on Thursday for his cross-check to the head of New York Rangers centre J.T. Miller on Tuesday night.
The play occurred late in the second period of Winnipeg's 3-2 loss to New York. Miller had fallen to the ice near the crease after taking a swipe at a rebound off the pads of Jets goalie Ondrej Pavelec. The 260-pound Byfuglien looked down at the prone Miller and drove his stick in to the back of the Rangers forward's head, also falling to his knees.
"Some measure of physicality in front of the net is common and acceptable, particularly when defencemen are attempting to protect their goaltenders," the league said in a video posted to NHL.com. "In this case, however, Miller is defenceless and out of the play by the time Byfuglien initiates contact."
The NHL's Department of Player Safety noted that when Byfuglien delivered the cross-check to Miller, Jets forward Mark Scheifele was already carrying the puck up ice, away from Winnipeg's net. The league's video on the incident characterized the blow as both "dangerous" and being delivered with "excessive force."
Other factors in the NHL's decision included the fact that Miller had no apparent injury and was able to complete the game and that Byfuglien had not been suspended but had been fined on three previous occasions over the span of his 596 game career.
Byfuglien learned of the ruling in a phone hearing on Thursday. Five-game suspensions are the maximum punishment the NHL can assign in a phone hearing.
The suspension could severely hurt the Jets' playoff hopes.
Winnipeg has lost its last two games and is just two points ahead of Los Angeles in the race for the Western Conference's second wild-card spot. The Jets have five games remaining in the regular season, while the Kings have six.
Byfuglien is a versatile player who has spent time as a forward and a defenceman this season. He has 18 goals and 27 assists with a plus-5 rating in 68 games this season.
Winnipeg hosts the Vancouver Canucks on Saturday.
The Jets have not made the post-season since moving to Winnipeg from Atlanta in 2011. The Thrashers only qualified for the post-season once, in 2006-07, and never won a playoff game.
Winnipeg has not hosted an NHL playoff game since the original Jets lost to the Detroit Red Wings in the conference quarter-final in 1995-96. The team moved to Phoenix that off-season, becoming the Coyotes.