Thomas Greiss replaced him with 4:22 remaining and the Islanders leading 2-1. Greiss stopped all three shots he faced to help New York win its fourth straight game.
Halak made 31 saves before leaving; he was credited with his 200th career win.
Islanders coach Jack Capuano did not have an update on Halak's condition after the game. New York visits the Toronto Maple Leafs on Wednesday.
Even with Halak injured, the Islanders still have two healthy goaltenders: Greiss and J-F Berube.
"I've got confidence if he does miss some time," Capuano said. "Berube's played great for us and Thomas has played extremely well too. We've got some quality goalies here and when you run into a situation [like this], hopefully it's not too long. But we've got confidence in the guys that we have here."
Greiss, who is 18-6-3 with a 2.20 goals-against average and a .930 save percentage, said he's prepared to be the No. 1 goalie if Halak misses significant time. Halak did not play until the Islanders' fifth game of the season because of an upper-body injury.
"It's happened before at the beginning of the year and I was helpful," Greiss said. "We have a good team. I think we'll be fine."
