TORONTO - The New York Islanders are likely to be without their No. 1 goaltender for the start of the playoffs.

Islanders head coach Jack Capuano announced before Wednesday's game against the Toronto Maple Leafs that Jaroslav Halak would miss the next six weeks with a lower body injury.

Halak was injured with less than five minutes remaining in the Islanders 2-1 win over the Pittsburgh Penguins on Tuesday night.

"It's a big loss for our team," Capuano said. "Guys are going to get an opportunity now to step in and hopefully can do the job."

That opportunity will fall to Thomas Greiss, the Islanders backup who actually leads the league with a .930 save percentage this season. Greiss, who owns an 18-6-3 record, was a winner in seven of eight starts before facing the Leafs on Wednesday.

Unlike Halak, who has 30 games of playoff experience, Greiss has gathered less than one full outing. He appeared in relief of Evgeni Nabakov for the San Jose Sharks in the spring of 2010.

"This is maybe something a little bit new for Thomas, too, moving forward," said Capuano. "I just know the kind of kid he is, the character that he has. He competes hard and that's what you look for in a goaltender."

Appearing in his second season with the Islanders, Halak has compiled an 18-13-4 record and .919 save percentage. Jean-Francois Berube will fill the backup role left vacant in his absence.

The post-season is due to begin on April 13, five weeks from the point of Halak's injury.

New York occupies the third spot in the Metropolitan division.