Fleury had two concussions in four months in 2015-16 while playing for the Pittsburgh Penguins and lost the No. 1 job to Matt Murray. He was 18-10-7 as Murray's backup last season and helped the Penguins win the Stanley Cup for a second straight season by going 9-6 in the Stanley Cup Playoffs before Murray returned from a lower-injury injury in the Eastern Conference Final.
Vegas selected Fleury in the NHL Expansion Draft.
Forward Jonathan Marchessault, who has one goal in four games, also was placed on injured reserve by the Golden Knights. He has a lower-body injury.
Vegas recalled goalie Maxime Lagace and forward Alex Tuch from Chicago of the American Hockey League.
The Golden Knights host the Boston Bruins on Sunday at T-Mobile Arena (7 p.m., ET; SN1, ATTSN-RM, NESN, NHL.TV). Goaltender Malcolm Subban likely will start for Vegas, with Lagace as his backup. Subban was selected by the Bruins with the No. 24 pick in the 2012 NHL Draft but was claimed by Vegas off waivers on Oct. 5.
