By the time he was 28, Greiss, a third-round pick (No. 94) by the San Jose Sharks in the 2004 NHL Draft, was already on his third team, the Pittsburgh Penguins. Prior to signing a two-year contract with the Islanders on July 1, 2015, he had never played more than 25 games in an NHL season.

EAST MEADOW, N.Y. -- As the years went by and New York Islanders goalie Thomas Greiss approached his late 20s, he rightfully wondered if he'd ever get the opportunity to be a full-time No. 1 in the NHL.

"At times, you doubt yourself," Greiss told NHL.com on Tuesday. "But in the end, it's what you work for. If you don't have that goal anymore, you don't believe very much. You've always got to battle every day and work hard every day and have that goal."

That belief has led to this opportunity that Greiss officially wrestled away from Jaroslav Halak at the end of December, when Halak was placed on waivers and sent to Bridgeport of the American Hockey League. One month later, Greiss, who could have become an unrestricted free agent this summer, agreed to terms on a three-year contract with the Islanders on Monday worth a reported $10 million.

Video: MTL@NYI: Greiss slides across to reject Pacioretty

"It's awesome. It's just gratifying," said Greiss, who is 14-7-3 with a 2.25 goals-against average and is fifth in the League with a .928 save percentage. "It just feels good. I'm just happy. Now the work starts and we've got to get the ball rolling here."

It will be on Greiss to help the Islanders in the race for a berth in the Stanley Cup Playoffs. New York, which is 4-0-1 since Doug Weight replaced Jack Capuano as coach on Jan. 17, is five points behind the Philadelphia Flyers for the second wild card from the Eastern Conference entering their game against the Washington Capitals on Tuesday (7 p.m. ET; MSG+, CSN-DC+, NHL.TV. The Islanders have three games in hand on the Flyers.

Judging by his history with the Islanders, Greiss has shown he has more than capable. He became the No. 1 last season when Halak sustained a lower-body injury in March and went on to help the Islanders win a playoff series for the first time since 1993, defeating the Florida Panthers in six games in the opening round.

"He means a lot," Weight said of Greiss, who went 23-11-4 with a 2.36 GAA and a .925 save percentage in 41 games last season. "Of course what he did last year … Jaro was having a good year and got injured. That can put a lot of teams out of a lot of situations, and Thomas stepped up and took the ball and really was our MVP late with [John Tavares] and was a huge part of advancing last year. Nothing's changed this year.

"In every situation, whether we had injuries, we had three goalies, he was playing, he wasn't playing, it's been professional. He works hard, he's a great kid, he's a big part of that room. More importantly to the onlookers, over the calendar year, 12 months, he's been in the top 20 percent of his goaltending fraternity. We're happy for him and happy for us. It's a great deal."

Until Halak was sent to Bridgeport, Greiss really had to fight for playing time; the Islanders were in an unusual situation of carrying three goalies on their roster with Jean-Francois Berube also in the mix. It was difficult for all three of them, but Greiss always took it in stride and performed at a high level nearly each time he was given a chance to play.

"He's got a real competitiveness, a real fire to him in the net," Tavares said. "You watch him practice and how long he stays out there to take shot after shot. I know how much pride he takes in stopping the puck and his expectations of himself. But he's a great guy to be around, a little laid-back so you've got to give it to him a little bit. He's been awesome."

Greiss' laid-back personality has rubbed off on his teammates during games and in the locker room. During the past 15 months, the Islanders have seemed to play with more composure, particularly in the defensive zone, with Greiss in goal.

"I think as we've gotten to know him over the last year and a half, he's certainly a huge part of our fabric for our team, both on and off the ice," defenseman Travis Hamonic said. "I think the last little while I've had an opportunity to watch some games like everybody else on TV objectively, and you really see how calm he is in net. You notice it when you're playing, but on TV you're like, 'Wow.' He's really calm and collected back there. When you're on the ice, that's a huge thing for our defensive core especially.

"He hasn't necessarily had this opportunity given to him in the past, and you see how hard he works. It's case in point that if I had a younger kid, I'd want them to see how hard you can work and you can get something. That's 100 percent what he's done. I think this is only going to make him work harder. We've relied on him a lot, and that's not going to be any different moving forward."

For Greiss, who turned 31 on Sunday, this newfound job security has to be one of the best birthday gifts he's ever received.

"It's exciting," Greiss said. "I've had a lot of success here and I'm happy to be able to stay here."