PITTSBURGH - For the Pittsburgh Penguins, one player - more than any other - is vital to their on-ice success against the Flyers.

He is a 24-year-old Canadian with a sparkling resumé that includes a Stanley Cup, multiple All-Star appearances and statistics that stack up with the best in his position in the NHL.

He missed a significant chunk of this season with postconcussion symptoms. He returned for a bit, dazzled to pull the Penguins out of a funk, and then was forced to sit out again later because of fogginess. His team struggled mightily without him.

His name is not Sidney Crosby.

In fact, many think the Penguins learned how to win without Crosby, who missed 107 games over the last two seasons and five against the Flyers alone. Instead, it's a lot tougher to explain Pittsburgh's marginal 18-13-0 record without Kris Letang this season.

The Penguins' two-pronged attack of Crosby and Evgeni Malkin deservedly garners the spotlight on a nightly basis. Quietly, some think Pittsburgh will go only as far as Letang - their horse on the back end - will take them in the playoffs.

"When he's out, we miss him, there's no question about that," Penguins forward Arron Asham said. "He's just as talented as any one of those guys [pointing around the locker room]."

To say the least, it was a tough season for Letang. Injuries are the only thing that have kept him out of the Norris Trophy race as the league's top defenseman. Even with the concussion and knee injury, which caused him to miss 31 games, Letang was nearly a point-per-game player, with 42 in 51 contests.

He finished second among defensemen in points-per-game to Ottawa's Erik Karlsson. Letang has 21 points in 28 career games against the Flyers.

But to single out Letang as simply an offensive dynamo would be to shortchange him.

"I've really seen his overall game develop," Penguins assistant coach Todd Reirden said on Saturday. "We have quite a bit of depth, both here and in [AHL] Wilkes-Barre, but none have the unique package that he does.

"He's a unique package of being able to add in the offensive zone, whether it's on the power play, or just getting a shot through most of the time. Then he's able to be able to defend with his feet. His pride with defending has changed quite a bit.

"His feet are great. His stick-on-puck is arguably one of the best in the league. When it comes time for him to play physical, he's got a great center of gravity down low. He can win battles down low against bigger, power forwards, and that's something that goes unnoticed."

Reirden, the former NHL player who heads the Penguins' defense under Dan Bylsma, said Letang's game has changed thanks to a daily video session that has quickly become a tradition. Letang and Reirden review game film together "for at least an hour" daily.

Even though plus/minus is a flawed hockey statistic, Letang finished this, his fifth full season, as a plus-21 playing against each opponent's top line nightly.

"The video has allowed him to slow the game down," Reirden said. "He's studied how to make himself better. Then he watches the top defensemen around the league."

Asham said Letang will "skate you into the ground." Letang averaged 24:50 in ice time this season, which Reirden said is "just a normal game for him." For the Penguins, any sense of normalcy is fleeting when Letang's familiar No. 58 is not meandering the blue line.

Pittsburgh lost six straight from Dec. 29 through Jan. 11. Letang returned on Jan. 19 and, not surprisingly, the Penguins went on to win five consecutive games; they had another 11-game streak from late February to mid-March.

"We saw our numbers on the power play drop quite a bit without him," Reirden said. "The minutes he can play are effortless. He takes a lot of pressure off our other guys."