Carter Hart left Wednesday night's game halfway through the first period with a mid-body injury and did not return.
After the Sabres grabbed a 2-1 lead, Hart was checked by head athletic trainer Tommy Alva for the second time in the period. Following a brief discussion, the 25-year-old goalie skated off under his own power and went up the Wells Fargo Center's home tunnel toward the dressing room.
Head coach John Tortorella didn't have any further update on Hart's status after the game.
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Hart has been excellent through the early going of the season. He entered the game 4-3-0 with a 2.30 goals-against average, .921 save percentage and one shutout.
Samuel Ersson took over in relief Wednesday night. He stopped seven of nine shots as the Flyers lost, 5-2.
"It's a tough game, don't get to see a ton of pucks," Ersson said. "But I just want to win, really. That's what it comes down to."
The 24-year-old has surrendered 14 goals on 59 shots in three appearances this season. The Flyers will need him to be better if Hart is to miss any time. It's possible more starts could help Ersson, who is in his first NHL season as a full-time backup.
"He's going to have to get sharp," Tortorella said. "I'm not sure what's Carter's situation. We'll find out more tomorrow. Sam has showed us many times that he can bounce back. I've listened to him talk to you guys, I think he self-evaluates very well. That's a really important part of a player — their self-evaluation. I think he's very strict with that, as far as how he feels about himself. I think that'll get him through it."