Halak last played March 8 because of a groin injury. J-F Berube was Greiss' backup during the playoffs.
"We look to improve our club, and I thought we did when we picked Berube off waivers," Islanders general manager Garth Snow said Thursday. "As it turns out, Jaro missed significant time during the season and it became a position of strength for us to have Thomas Greiss, the way he performed during the season and the playoffs, and to have Berube come in and really solidify that position was a positive for our club. Moving forward, we will have to make decisions."
Greiss, 30, was signed before the season as Halak's backup. But Greiss started an NHL career-high 41 games, going 23-11-4 with a 2.36 goals-against average and .925 save percentage.
"[Greiss] proved to be a No. 1 goalie in the League this season," Snow said. "Thomas came in and displayed a great work ethic whether he was playing or whether he was backing up on a certain night. I think Thomas earned the respect from our players, from our coaches because of his personality, his demeanor, his work ethic. And when he got the opportunity to play, he seized it and he played great for us."
Halak, 30, went 18-13-4 with a 2.30 GAA and .919 save percentage in 36 games. He said Tuesday that it was not ideal playing in a three-goalie system.
Halak has two years remaining on his contract, Greiss has one and Berube will be a restricted free agent July 1.