Ottawa has beaten the Panthers five straight times in Florida and 17 of 20 on the road.
"I don't know if they feel that we have an advantage on them or not," Alfredsson said. "In today's NHL, we've just got to go out there and work hard for 60 minutes no matter who you play. You can't think, 'This is going to go our way.' You're going to have to work for it."
Florida allowed six goals at home for the first time this season, but set a season high with 44 shots. The Panthers were shooting for their first four-game winning streak in four years, but didn't come close.
"We had a decent first period, but in the second, bang-bang. A couple goals against, and the rain kept falling from there," Panthers coach Kevin Dineen said. "A very disappointing game in front of our home fans."
Ottawa took a 2-1 lead in the second. Brian Lee sent a pass from above the right circle to Daugavins, who tipped the puck in from in front at 5:18.
The lead grew to 3-1 a couple minutes later when Michalek passed from the top of the left circle to Butler, who deflected the puck past Clemmensen's glove side at 7:24.
Alfredsson's short-handed goal at 14:06 of the second made it 4-1. The Panthers turned the puck over in the neutral zone, and Alfredsson skated in and backhanded the puck over the goalie's pad. Clemmensen was then replaced by Theodore.
"That's the good thing about breakaways compared to shootouts or penalty shots. You don't have too much time to think," Alfredsson said. "I didn't have the shot, so I just tried to fake and go on my backhand. It worked out pretty good."
The Senators kept pouring it on, and Michalek pushed the lead to four goals. Bergenheim's power-play goal later in the third closed the gap to 5-2.
Kuba added a power-play goal for Ottawa late in the period.
"You don't score six in a game, you don't continue to win if you don't get contributions from everybody," Senators coach Paul MacLean said.
Three of Ottawa's goals came on tip-ins.
"All their point shots, they're not shooting it for the net shots, they're shooting it for tips and deflections and they're trying the back door plays," Clemmensen said. "It's tough to absorb that, and trying to make a push ourselves."
Ottawa went ahead 1-0 on O'Brien's goal. O'Brien, recalled by Ottawa on Feb. 3, took control of the puck behind the net and poked it in on a wraparound at 5:35 on the first.
"It was more of just relief," O'Brien said about his first goal. "It was kind of building up there and it was just a great feeling. It's even better that we got the win."
The Panthers tied it when Matthias sent a wrist shot from the left circle over Anderson's shoulder at 11:47.
Florida D Jason Garrison will be out seven to 10 days because of an undisclosed lower body injury sustained Saturday against New Jersey. ... Matthias has four points in four games. ... Bergenheim has seven points in eight games. ... Ottawa's Butler has one goal and five assists in four games. ... Ottawa C Jason Spezza has five goals and seven assists in five games. ... Alfredsson has three goals and four assists in three games against the Panthers this season. ... The Senators are in the midst of their annual Father's Trip, with 17 fathers of players in attendance.
Copyright by STATS LLC and The Associated Press
Arena: BB&T Center Location: Sunrise, Florida
Referees: Kevin Pollock, Ian Walsh Linesmen: Greg Devorski, Brad Kovachik
Attendance: 14,038 (72.9% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Jim O'Brien (1)
Assists: Nick Foligno, Brian Lee
Shawn Matthias (10)
Assist: Mike Weaver
Kaspars Daugavins (4)
Assists: Brian Lee, Erik Condra
Bobby Butler (6)
Assists: Milan Michalek, Jason Spezza
Daniel Alfredsson (20)
(Shorthanded) Assist: Kaspars Daugavins
Milan Michalek (25)
Assists: Erik Karlsson, Jason Spezza
Sean Bergenheim (12)
(Power Play) Assists: Brian Campbell, Tomas Fleischmann
Filip Kuba (5)
(Power Play) Assists: Jason Spezza, Daniel Alfredsson