Hischier scored twice and had an assist, Dawson Mercer had a goal and an assist, and Hughes had two assists for the Devils (42-36-3), who won their second straight game after losing two in a row. Nico Daws made 27 saves in his second start of the season and first since a 4-1 win against the Minnesota Wild on Oct. 22.
"Anytime you're in this League, it's fun to start, and winning games is even better," Daws said. "I just have that mindset of this is the League I want to play in and that's what I'm working for."
Michael Amadio, Shane Pinto and Fabian Zetterlund each scored, and Reimer made 26 saves for the Senators (43-27-11), who are one point behind the Boston Bruins, each with one game left to play, in the wild-card race.
"We had a good second (period) and I thought we could have won. ... (Reimer) made some big saves for us," Pinto said. "We started out a little slow, but overall, not a bad game."
Ottawa played without forwards Brady Tkachuk (illness) and Tim Stutzle, as well as defensemen Jake Sanderson and Thomas Chabot.
"We have been through a lot this season," Senators forward Claude Giroux said. "We dug ourselves into a pretty big hole and we were able to get out of it, find a way to make the playoffs. (Saturday) was a great day and it was great that we were all together, and kind of see the excitement of the guys and how we're pumped to be back in the playoffs."
Hischier gave the Devils a 1-0 lead when he cleaned up a rebound from the slot at 5:12 of the first period.
"That game didn't matter (since we cannot qualify for the playoffs), but it matters ... if that makes sense," Hischier said. "I think it's very important for us to finish strong this season. We're not happy where we're at and we came up way short. It's just giving something back to our fans, that's the least we can do."