NHL

Rangers have interest in Kuba to help defense

If the Ryan McDonagh-Michael Sauer partnership represented the Rangers’ third pair on defense, the team would be whistling while they work their way to the playoffs through the season’s final 24 games.

The problem, however, is that the rookie tandem has evolved into the team’s second pair behind Marc Staal and Dan Girardi, thus leaving John Tortorella without fifth and sixth defensemen he particularly trusts.

Sunday, for instance, Matt Gilroy, who has lost his position on the power-play point, played 7:49 overall and 3:20 in the third while partner Steve Eminger never got off the bench in the third period of the 5-3 victory over the Penguins, finishing with 4:08.

McDonagh played a total of 20:43 and Sauer, 20:17, about a minute over their per-game averages (Sauer 19:29, McDonagh, 19:13) since they were united six games ago. It’s a lot of responsibility for a pair of rookies who have a combined 72 games of NHL experience.

“I have to make calls [based] on who’s playing [well],” said Tortorella, who will insert Michael Del Zotto into the lineup tonight at the Garden against the Kings in place of Eminger, who will sit for the sixth time in seven matches.

“I wouldn’t like to [have the same discrepancy in ice time] with three games coming up in 3 ½ days [tonight; at New Jersey tomorrow night; vs. the Flyers on Sunday afternoon]. I’d like to try to spread it out a little bit here.”

With the trade market humming in advance of the Feb. 28 NHL deadline, general manager Glen Sather is on the lookout for a defenseman in order to give his coach alternatives.

The Post has learned the club has at least some interest in Ottawa’s 34-year-old, 10-year veteran Filip Kuba, who played for Tortorella in Tampa Bay in 2006-07 and 2007-08 after spending four years in Minnesota with Marian Gaborik.

Kuba is averaging 19:15 per game, the lowest ice time of his career. The 6-foot-4, 229-pound native of the Czech Republic is a big body defender with a big shot from the point. Indeed, Kuba scored a career-high 15 goals while playing for Tortorella in his first year with the Lightning. He’s getting 1:41 per game on the power play for Ottawa.

The Senators, who dealt Chris Kelly to the Bruins for a No. 2 on Tuesday night, are dismantling. The price for Kuba is unlikely to be exorbitant; he has one more year remaining on his contract at a salary-cap hit (and cash price) of $3.7 million.

That charge isn’t a problem now for the Rangers, who currently have a full-season value of approximately $8.4 million to spare. But it could be an issue as it relates to the 2011 summer cap.

Even if the summer cap is close to $70 million, the Rangers have to be careful if they intend to be in on free agent Brad Richards, which they most certainly do.

The Rangers have about $41.1 million on the summer cap, including $6.5 million for Wade Redden but not including a nickel for Group II free agents Ryan Callahan, Brandon Dubinsky, Brian Boyle, Artem Anisimov and Sauer, who likely will combine for $13-15 million.

That $41.1 million number also does not include Chris Drury, who will be in at $7.05 million if he remains on the roster, or $3.717 million if there’s a June buyout.

larry.brooks@nypost.com