PITTSBURGH — Pavel Buchnevich has no structural damage to his back, according to the results of an MRI, Alain Vigneault said Monday, but the rookie forward will be put on a program to strengthen his core muscles to prevent a recurrence of the back spasms that have sidelined him for all but 10 games this season.

“Our doctors decided to put him on a two- to three-week rehab to reinforce the core. We feel that with that, there should be no issues within three weeks,’’ Vig neault said. Asked about the cause of the issue, he smiled and said: “Russian training? I don’t know. You see him walking around, I think it’s pretty evident that he’s been playing hockey with that high skill level. Like any young player, he needs to develop physically, he needs to develop his upper body, lower body, and right now, especially his core strength. Nothing against Putin.”

Buchnevich, 23, who is 6-2 and listed at 193 pounds but appears slimmer, came to New York during the summer to start training and learn more about nutrition and English. He has missed the last five games and five in October, and has four goals and eight assists in the others.

With Buchnevich and Mika Zibanejad (broken left leg) out, the Rangers claimed left wing Matt Puempel off waivers from Ottawa. “It’s a combination of both of those things,” general manager Jeff Gorton said. “He’s a guy we’ve scouted in the past, a guy who likes to shoot the puck, can score goals [30 three times in juniors], and we have a spot on our team right now. The timing’s right.”

Although Puempel, 23, a first-round pick in 2011, played center in juniors, Gorton said he’s “more of a wing, a power-play guy, skill guy. The opportunity was there to get a player that our scouts think highly of. There’s not a lot of downside, we’ll take a look and see where he fits and then make a decision on him.”

Puempel, who was 4-2-6 in 54 games for Ottawa in parts of three seasons, will be available to play Wednesday night.

Gorton confirmed that Zibanejad does not need surgery. It’s a non-displaced fracture, similar to Derek Stepan’s three years ago.

Blue lines

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Ryan McDonagh became the first Ranger to post a plus-five rating since Marian Gaborik on Nov. 14, 2010, against the Oilers and the first defenseman to do so since Darius Kasparaitis on Dec. 26, 2003, against the Maple Leafs. With 13 assists, McDonagh is second among NHL defensemen this season . . . Antti Raanta is the first Rangers goaltender who has earned a win in each of his first five decisions since Steve Weeks in 1983-84, according to the Elias Sports Bureau . . . With three shorthanded goals, the Rangers lead the league in that category; they had three all of last season . . . The Blueshirts are 6-2-0 when they allow the first goal of the game, and the .750 winning percentage is tops in the NHL . . . Defenseman Adam Clendening was a healthy scratch . . . Henrik Lundqvist is expected to be in net for the second half of the home-and-home with the Penguins on Wednesday night.