The Rangers’ first-round opponent is a familiar foe — the Pittsburgh Penguins.

The Islanders lost to the Flyers, 5-2, on Sunday night, which clinched third place in the Metropolitan Division for the Rangers, who will meet Sidney Crosby and the Penguins in the playoffs for the third straight season and in the first round for the second straight season.

Last season the Rangers won in five games. The year before, the Rangers rallied from a 3-1 deficit to knock out the Penguins in seven games, including a Game 7 in Pittsburgh.

Led by a former Rangers assistant coach, the Penguins have been marching. Not in Antarctica, but through the NHL.

Since Dec. 12, when Mike Sullivan took over behind the bench, the Penguins have gone 33-16-5. Sidney Crosby, who had 19 points in the first 28 games, stands at 36-49-85. With a more offensive approach under Sullivan, John Tortorella’s assistant in New York, they have 240 goals, third-best in the NHL, and have won 13 of the last 15 games.

The Penguins, 2-1-1 against the Rangers this season, are missing two major components. There is no timetable for goaltender Marc-Andre Fleury’s return from concussion symptoms; he last played March 31. Center Evgeni Malkin, with 58 points in 57 games, has missed nearly a month with an upper-body injury.

Perhaps the most impressive trio has been center Nick Bonino with Phil Kessel and former Ranger Carl Hagelin. Kessel, with a deadly accurate shot, and Hagelin, acquired by general manager Jim Rutherford from the Ducks on Jan. 16, have great speed, and with Bonino, whose forte is retrieving pucks, they have been dangerous. Along with Crosby’s linemates, Patrick Hornqvist and Chris Kunitz, the Penguins have a formidable top six.

On defense, Kris Letang is having a Norris Trophy-worthy season, with 16 goals and 67 points. But beyond Letang, the Penguins aren’t deep, especially with the uncertain status of Olli Maatta, who has missed the last two weeks. If Fleury cannot return, goaltending duties are in the hands of 6-4 Matt Murray, 21, a terrific prospect who has played only 13 NHL games.