Fleury had made four starts, going 3-1 with a 2.48 goals-against average, before taking a hit to the head against Detroit. The injury was at first not thought to be serious, but Fleury has a history of concussions.
The Golden Knights have been the surprise of the NHL this season. The expansion club is second in the Pacific Division with 39 points.
The success comes despite losing Fleury, the top player taken in the expansion draft, and his backup Malcolm Subban for parts of the season due to injury.