Ottawa forward Mike Hoffman was asked by his coach to shut down Sidney Crosby. Outscoring Pittsburgh's captain was a bonus.
Hoffman scored the eventual winner while Mike Condon made 29 saves as the Senators downed the Penguins 4-1 on Thursday.
"The whole idea with Mike is he's got the speed to skate with anybody in this league," said Ottawa coach Guy Boucher.
"Since the beginning of the year he's definitely progressed defensively. It doesn't take away from his offence as he scored again tonight and he's got I don't know how many shots, but he played terrific and when you see players like that growing and becoming really good two-way players you know your team is going in the right direction."
In addition to Hoffman, Bobby Ryan, Tom Pyatt and Mark Stone also scored for Ottawa (22-14-4).
Not only did the Senators avenge an ugly 8-5 loss to the Penguins last month, they handed the defending Stanley Cup champions their first back-to-back regulation-time losses since Dec. 14-19, 2015.
Conor Sheary scored the lone goal for the Penguins (26-10-5) as Matt Murray, playing for the first time since suffering a lower-body injury Dec. 28, made 29 saves.
The Penguins didn't make excuses for their play.
"I would have liked to see that streak continue, but sometimes you need to lose a couple in order to play better," said Crosby.
"We haven't deserved to win the last couple games and sometimes when you're playing well you get some bounces given and good teams find ways to win games that they're not their best, but we didn't deserve to win the last couple so we've got a find a way to get back on track here a bit."
Holding a 3-1 lead to start the third, Ottawa held off the Penguins and midway through the period put the game out of reach as Stone scored his 13th of the season in front of 17,769 at Canadian Tire Centre.
"We stuck with it the whole game and we've been struggling this year having the lead going into the second and I think we cleaned most of it up this game," said Senators captain Erik Karlsson, who picked up two assists while playing a season low 21:36.
"They're a good team and they got their quality scoring chances and we got some big stops when we needed it and I think we just stuck with it all the way to the end."
Frustration was clearly setting in for the Penguins as coach Mike Sullivan was given a game misconduct and ejected with just under two minutes remaining.
"I think we need to recognize when we don't have our best," said defenceman Ian Cole. "Maybe we need to play more of a territorial game, stop trying to beat guys one-on-one, which we can do when we're at our best, but when we don't have our legs and our jump maybe we need to play a little bit smarter."
Condon was at his best in the second, making a number of big saves, including one on Phil Kessel and another on Nick Bonino. He also got a little help when Scott Wilson rang a shot off the post.
Leading 2-0, Ottawa was able to extend its lead midway through the period as Pyatt re-directed Karlsson's shot over Murray's right leg.
The only blemish for Condon was giving up a goal with 6.4 seconds remaining in the second when Sheary tipped Evgeni Malkin's shot to get the Penguins on the board.
The Senators couldn't have asked for a better start to the game.
Ottawa opened the scoring with a power-play goal at 5:29 as Ryan scored his eighth of the season, beating Murray through the legs. Less than four minutes later the Senators made it 2-0 as Hoffman had a perfect re-direct on Karlsson's point shot.
Notes: The Senators remain without G Andrew Hammond (ankle) and Clarke MacArthur (concussion). D Fredrik Claesson was a healthy scratch. Pittsburgh D David Warsofsky and C Eric Fehr were healthy scratches.
Lisa Wallace, The Canadian Press