PITTSBURGH — If you thought the Rangers had an uphill climb against the surging Penguins, that mountain just got steeper.

In an early double blow to any Stanley Cup dreams, Henrik Lundqvist suffered an injury near his right eye late in the first period last night and was replaced by backup Antti Raanta, and the Rangers couldn’t solve substitute goaltender Jeff Zatkoff.

Zatkoff, playing in his first NHL post-season game, stoned the Rangers for the first two periods and they dropped Game 1 of the best-of-seven first-round series, 5-2.

Rangers coach Alain Vigneault provided little information on Lundqvist, other than saying he did not believe Lundqvist was checked out at a hospital, just by medical staff at the arena. “I saw him between the second and third . . . He’ll be re-evaluated tomorrow. We should know more tomorrow.”

While battling with Oskar Sundqvist to the right of the crease, Marc Staal’s stick accidentally clipped Lundqvist under the mask with 48.2 seconds left in the first, and the goaltender went down, holding his face.

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“It’s one of those things that happens,” said Staal. “I didn’t know where I got him. Anytime he goes out like that, it’s not a good sign. I hope he’s all right.”

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Trainer Jim Ramsay came out and Lundqvist eventually rose, with the crowd at Consol Energy Center booing, and skated to the bench for water. When play resumed, Conor Sheary took a sharp angle shot from Lundqvist’s right that bounced in front where Patric Hornqvist wristed the puck in with 17.6 seconds left, the first of his hat trick last night.

Zatkoff, 28, had stepped on stage when Marc-Andre Fleury, who practiced in the morning but hadn’t played since March 31 after sustaining a concussion, was scratched. He finished with 35 saves, 12 in the first period when the Rangers generated most of their shots in the first 10 minutes.

Down 2-0 in the third after Sidney Crosby’s breakaway goal with 1:04 left in the second, the Rangers were more desperate. Zatkoff was saved by a post, and made a blocker save on Eric Staal coming down the right side. Carl Hagelin high-sticked Kevin Hayes and drew blood for a double-minor and Ian Cole interfered with Staal.

Derek Stepan scored on the 5-on-3 at the left post at 3:10 to cut the lead in half and Chris Kreider just missed tying the game when his shot hit the crossbar on the 5-on-4. Moments later, Nick Bonino found Tom Kuhnhackl on a shorthanded 2-on-1 with only Keith Yandle back to restore the two-goal lead.

“That was definitely a turning point,” said Vigneault. “We had two players who didn’t take a stride to come back and Yands didn’t play the 2-1 the way he’s supposed to. He’s supposed to have that pass.”

Said Stepan: “It’s a backbreaker.”

Hornqvist scored his second on a power play at 8:02 when he poked in a loose puck with Phil Kessel already in the crease. Vigneault challenged the call, but the goal stood. Stepan’s second came at 10:11 on a rebound at the right post. Hornqvist ended his night with an empty-netter at 17:10, and the Penguins, who had won 14 of their last 16 games down the stretch, had sent the Blueshirts to regroup for Game 2 on Saturday.

“There’s a few things that we can build on, but I do know we’ve got quite a few guys who need to play better than they did tonight,” said Vigneault.

And they may have to do it with Raanta, who allowed three goals on 19 shots in relief, rather than Lundqvist, the team’s emotional leader and MVP, in the nets.