Lemieux, sidelined for the series opener, scored two goals Saturday night as the defending champions won the Wales Conference title, capping a four-game sweep of the Boston Bruins with a 5-1 victory.
"He's the best player in the league," Boston's Ray Bourque said, "one of the greatest if not the greatest ever to play the game."
Said Boston's Dave Poulin: "It's almost scary. It looks like he's toying with you, like he can turn it on at any moment. That's how good he is. When he's out there he creates so much room for the other guys. He opens things up for them."
Lemieux, hurt in the previous series when he was slashed by Adam Graves of the New York Rangers, opened the door to the Stanley Cup finals. They begin Tuesday night in Pittsburgh against the Chicago Blackhawks.
Chicago swept Edmonton, only the second time in best-of-seven semifinals that both finalists advanced with sweeps. Boston and the New York Rangers did it in 1972, when the Bruins won their last Stanley Cup.
Boston had played Pittsburgh evenly in the opener, but lost by 4-3. Lemieux, who said he didn't expect to return until the fifth game, came back in Game 2 and made sure there was no fifth game.
"He wanted to play (Game 2) and it made a lot of sense for me," Penguin Coach Scotty Bowman said. "You don't want to take a chance of losing a home game and, as it turned out, he kept getting better and better."
Said Bruin Coach Rick Bowness: "All of a sudden we were in awe of Mario Lemieux and it changed the whole series around."
Jaromir Jagr scored 4:51 into the game, and the second goal, at 13:09 of the first period, was all Lemieux.
Boston had a man advantage, and Joe Juneau had the puck in the right corner of the Penguins' zone. He tried to pass to Bourque at the left point, but the 6-foot-4 Lemieux stretched his right arm and intercepted the puck in the right circle.
He skated up the middle, evaded Bourque near the Boston blue line and flipped a forehand shot into the upper right corner of the net.
"He's the only one who can do that," teammate Kevin Stevens said.