Mike Comrie scored his 14th goal 8:10 into the third on a 5-on-3 and Dean McAmmond got his seventh at 14:50 as Ottawa went on to win its third in a row.
Florida's Ed Belfour stopped 29 shots one night after making 29 saves in a 1-0 win in Montreal to record his first shutout in nearly three years -- the 76th of his career, tying Tony Esposito for eighth place on the NHL career list.
Gerber lost the starting job in mid-November to Emery, who began a three-game NHL suspension for striking Montreal's Maxim Lapierre in the face with his stick Saturday.
After leaving Stanley Cup champion Carolina as a free agent, Gerber started 3-8-1 with the Senators.
"He's a big part of our team, and for him to get back in there and have a game like tonight is not only big for him personally, to go and do that, but for the club as well," Phillips said.
Stephen Weiss hit the post in the first period on one of the Panthers' few real scoring opportunities. Florida outshot the Senators 15-13 in the frame, though most of the drives were from the outside as they were throughout the game.
"A lot of the shots we had from outside were right in his belly, and we didn't get a lot of rebounds," Weiss said. "When there were rebounds we just didn't have enough guys in front of the net and we weren't hungry enough in front of the net, that's basically it. We weren't buzzing enough. I think we were just too cautious about getting caught."
Ottawa opened the scoring 8:21 in when Phillips circled behind the Panthers' net before putting a shot in off Belfour's pad.
Fisher beat Belfour with a quick shot from the slot after Peter Schaefer stripped the puck from defenseman Ruslan Salei behind the net.
"We wanted to get on them fast because they played last night," Fisher said. "Gerber played solid. He played really well for us and he was very calm back there. He made it easy for us."
Panthers C Chris Gratton had a spirited fight with Fisher midway through the first. ... G Kelly Guard was Gerber's backup. Guard, who has yet to make his NHL debut, dressed for four games from Nov. 7-15. He is 9-16-3 with a 3.38 goals-against average in 31 games with Binghamton of the AHL this season.
Copyright by STATS LLC and The Associated Press
Arena: Canadian Tire Centre Location: Ottawa, Ontario
Referees: Stephane Auger, Chris Lee Linesmen: Don Henderson, Tim Nowak
Attendance: 18,561 (100.3% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Chris Phillips (8)
Assists: Antoine Vermette, Chris Kelly
Mike Fisher (11)
Assist: Peter Schaefer
Mike Comrie (14)
(Power Play) Assists: Dany Heatley, Jason Spezza