The Rangers' Adam Fox is injured during the third period against...

The Rangers' Adam Fox is injured during the third period against the Tampa Bay Lightning at Madison Square Garden on Nov. 29. Credit: Getty Images/Bruce Bennett

GREENBURGH — Replacing Adam Fox, who will be on long-term injured reserve with an upper-body injury until at least Christmas, is proving to be no easy task for the Rangers and coach Mike Sullivan.

They managed to win their first two games without their top defenseman, a former Norris Trophy winner, and went 2-0-2 in the first four games without him. That included back-to-back stellar efforts in overtime losses to two of the league’s most elite teams, Colorado and Vegas.

But a 3-0 loss to Chicago on Wednesday made it clear how much the Rangers really miss the Jericho native. He is their second-leading scorer and the point man on their power play. And while the rest of the defense corps has done well to make up for Fox’s absence on the defensive end, the Rangers don’t have a backup option to play the point. Not coincidentally, they’ve gone 0-for-12 on the power play in the five games Fox has missed.

Without Fox, Sullivan has used a first power-play unit composed of five forwards. It’s an unconventional look, as most teams go with four forwards and one defenseman, but a few teams, such as Vegas, do run a five-forward power play.

“I’ve never done it before until this year,’’ J.T. Miller said of a five-forward power play. “It’s new. It’s a hard position to play up there. So I know [Artemi Panarin] and Mika [Zibanejad] are trying to obviously learn it. Foxy is such a big piece of our power-play unit, and the little nuances that he has in his game that help us so much.’’

The risk in not having a defenseman at the point is that, in the event of a turnover, there isn’t a defender who can drop back and defend a shorthanded two-on-one break. Against Chicago, a fumbled puck at the point in the second period led to a shorthanded goal that put the Rangers behind 1-0. After that, Sullivan put rookie defenseman Scott Morrow at the point for the two power plays the Rangers got in the third period.

“Foxy is not an easy guy to replace,’’ he said after the game.

On Friday, Sullivan went back to the five-forward setup at practice, with a couple of tweaks. Zibanejad was installed at the point, replacing Panarin, who shifted over to Zibanejad’s spot on the left wing boards. Alexis Lafreniere was elevated from the second unit to replace Will Cuylle at the netfront position on the first unit.

“We think they’re the best five guys right now,’’ Sullivan said of the five-forward look. “We moved them in different positions. We made some adjustments.’’

Sullivan said when the idea of the five-forward power play first came up, Panarin and Zibanejad seemed the best candidates to fill in for Fox at the point. Part of the reason they chose Panarin for the job, he said, was the fact that they like having Zibanejad, who has a hard shot, still available to take one-timers from the left side.

But because Zibanejad is a better defensive player than Panarin, Sullivan reasoned he “might add a little bit more of a defensive conscience’’ at the point. Zibanejad also is more of a shooting option from there than Panarin or even Fox.

“We can create different ways,’’ Sullivan said. “We can create off the shot, too. I think we have to have more of a willingness to shoot the puck and put a puck in play and then create off the shot. If the first one doesn’t go in, it’s going to present [a rebound] opportunity for a next play.’’

Notes & quotes: Saturday’s game against Montreal is another of the Rangers’ Centennial nights in which the team will wear its Centennial jerseys. The theme Saturday will be “The New Garden’’ era, highlighting the seasons between 1967 and 1991.

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