In a devastating blow to the Rangers’ offense, center Mika Zibanejad will be sidelined six to eight weeks with a broken left fibula after sliding awkwardly into the boards in overtime in the Rangers’ 3-2 shootout loss to the Florida Panthers on Sunday night at Madison Square Garden.

Zibanejad, 23, who arrived from Ottawa in the Derick Brassard trade last summer, lost his balance while skating behind the net with Reilly Smith early in the extra session. His left leg bent up and into the boards, and he was writhing on the ice as trainer Jim Ramsay raced off the bench. Zibanejad was helped off by Chris Kreider and Mats Zuccarello.

“He was in a lot of pain,” Henrik Lundqvist said after the Rangers lost their second in a row for the first time this season. “You could hear him. It was not a good sign.”

In the shootout, Vincent Trocheck scored through Lundqvist’s legs and Aleksander Barkov netted the winner. Lundqvist (28 saves) made the initial stop, but the puck slid slowly across the goal line before he could pull it back with his glove.

“I knew it was a close call,” he said. “I thought I had it and it would stop, but it just kept going. It’s frustrating.”

Zuccarello and Brandon Pirri were stopped in the shootout by Panthers goalie James Reimer, who made 33 saves.

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Rangers coach Alain Vig neault said the team will replace Zibanejad — who scored his fifth goal Sunday night to go with 10 assists — with Oscar Lindberg, the only other healthy forward, for Monday night’s game against the Penguins in Pittsburgh.

Zibanejad certainly will be placed on injured reserve. Vigneault said Josh Jooris, Pirri and Lindberg, a healthy scratch Sunday night, are options at center, and another center could be summoned from AHL Hartford soon.

The devastating blow overshadowed a game in which the Rangers lost two one-goal leads and didn’t really test Reimer enough after the first period, when they had 14 shots and took a 1-0 lead on Kreider’s high, short-side wrist shot from the left circle off a rush.

Although the ice was poor, with the Knicks having played in the afternoon, the Rangers had good looks but simply passed it around too much. A team that was averaging more than four goals a game has scored only four in the last two games, plus an overtime.

“When the ice gets junky like that, you have to get it to the net,” defenseman Marc Staal said. “We really didn’t get enough second opportunities.”

In the second period, after a third Rangers power play sputtered, Brady Skjei covered the puck in the defensive zone, and it didn’t take the Panthers long to tie the score.

Former Ranger Keith Yandle’s slap shot from the left point flew past Lundqvist for his first goal of the season at 14:43.

In the third period, Zuccarello spun away from the net but flipped a backhander toward the crease, where the puck went through defenseman Aaron Ekblad’s legs, off a falling Zibanejad’s skate and past Reimer at 1:45.

Ekblad’s 45-foot shot hit the leg of J.T. Miller skating by, bounced down off the ice and went past Lundqvist to tie the score at 2 with 12:06 left.

Said Lundqvist, “He’s trying to get there with his stick, but obviously, it fooled me a little bit.”