The Buffalo Sabres halted the Penguins' march toward NHL history on Tuesday, beating Pittsburgh 4-1 to snap the Pens' winning streak at 15 games.
The Penguins were closing in on their own NHL record of 17 consecutive wins, set during the 1992-93 season.
But with star Sidney Crosby sidelined after being hit in the face by a puck on Saturday, the Penguins lost for the first time since a 4-1 setback against Carolina on February 28.
Pittsburgh's 15-game streak matched the New York Islanders' run from January 21 to February 20, 1982 as the second-longest in league history.
Kevin Porter notched his first two goals of the season to help support a 19-save effort from Sabres goalie Ryan Miller.
"Hopefully this is something we carry forward," Miller said of the win.
Steve Ott and Cody Hodgson also scored for a Buffalo team that had lost four in a row and are last in the Northeast Division.
The Penguins had built their streak despite the absence of Russian star Evgeni Malkin for 10 of those games with a concussion and shoulder injury.
Top goaltender Marc-Andre Fleury and defenseman Kris Letang missed multiple games during the run.
But Crosby's broken jaw, which will have the Canadian star sidelined indefinitely, proved too much to overcome.
"All in all, we just weren't very good," Penguins defenseman Matt Niskanen said. "The execution was poor. Battle level was poor."
Recently acquired Jarome Iginla scored his first goal as Penguin, but it wasn't enough.
"At the time it felt good to get my first as a Penguin... but it's a disappointing feeling now because I know these guys had worked hard at this streak," Iginla said.
Pittsburgh goalie Tomas Vokoun, who had back-to-back shutouts in the Penguins' last two games, stopped nine of 13 shots before he was pulled in favor of Fleury early in the second period.