The Lightning will be without goaltender Andrei Vasilevskiy for four to six weeks because of a fractured left foot.
The team got that assessment Friday after Vasilevskiy, hurt during Wednesday's practice in Pittsburgh, was evaluated by its doctors in Tampa.
This means the Lightning will be without one of its best and most important players for at least 14 games on the four-week end of the estimate.
The team had no further comment.
Louis Domingue will start for Vasilevskiy, who entered Friday tied for second in the league in wins with nine. Vasilevskiy, a Vezina Trophy finalist last season, is 9-3-1 this season with a save percentage of .927 (11th in the league) and a goals-against average of 2.29 (ninth).
Coach Jon Cooper said Thursday that he feels good with Domingue in net.
Against the Penguins on Thursday, Domingue made 28 saves on 31 shots in the 4-3 win. He also started the 2-1 loss to the Sabres on Tuesday, a planned night off for Vasilevskiy. Those were Domingue's first consecutive starts of the season. His third straight start would be at 1 Saturday afternoon against the Flyers at Wells Fargo Center.
Eddie Pasquale was called up from AHL Syracuse to back up Domingue.