Thomas Greiss is a rarity in the NHL: A low-key goaltender. The 30-year-old’s German-accented English comes out in one long shrug, better suited to a surfer than to a member of the high-strung goaltender community.

That attitude will get its toughest test starting on Thursday, when Greiss starts his first NHL playoff game as the Islanders’ No. 1 goaltender. Jaroslav Halak isn’t close to returning and youngsters J-F Berube and Christopher Gibson aren’t ready for prime time, so it’s Greiss’ net.

“Thomas has really had a great year, first half he was so crucial for us,” John Tavares said on Tuesday. “He’s not a character, but a bit of a laid-back guy, great approach to the game, great attitude. There’s really not a mindset change for him.”

That was the same goal Greiss had when Halak went down with a serious groin injury on March 8. Greiss had been arguably the better goaltender all season as Halak struggled with a couple of poor outings and atrocious goal support and Greiss, signed on July 1 to a two-year deal to be Halak’s backup, played surprisingly well.

But being the one in the spotlight can change things. Greiss had been leading the NHL with a .930 save percentage on March 8; in 13 appearances after that date, Greiss posted a .914 save percentage and was 5-5-1.

Fortunately for Greiss and the Islanders, his best stretch has been down the stretch. He won four of his last five starts and allowed only seven total goals in those four victories.

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He finished the season with 41 appearances, far more than his previous career high of 25 with the Coyotes in 2013-14, and a .925 save percentage, also a career best.

“Most games played ever for me, that’s a good thing,” he said. “Keep it going into the playoffs, keep the rhythm going.”

That rhythm will be tested with Games 1 and 2 coming on consecutive nights. Jack Capuano has bought into the statistical analysis that shows playing the same goaltender two nights in a row is usually a mistake and hasn’t started the same goaltender in any back-to-backs this season.

But this is the postseason, when emotion and hunches can push the data aside. “With the goalies, there’s always that question,” Capuano said. “Goaltending is a decision we’ll have to sit down and evaluate after Game 1.”

Greiss noted this is not a typical back-to-back situation. “You focus on the first game, just worry about the second game after. You don’t have to travel so that definitely makes life easier, just go back to the hotel after,” Greiss said. “It’s a little different.”

So is this postseason. Greiss will be the third different goaltender to start Game 1 for the Islanders in their three playoff appearances the past four seasons, with Evgeni Nabokov and Halak in net the past two trips.

Halak skated on Tuesday on his own, but Capuano said there’s very little chance he will be ready for any part of this series. So Greiss, with 40 minutes of playoff experience, gets the call.

“You just don’t overthink it,” Greiss said. “I’ve played a pretty good amount of games this year so it’s not going to be different.”