Matthew Tkachuk had a goal and three assists, Carter Verhaeghe had two goals and an assist, and Seth Jones had three assists for Florida (36-35-3), which had lost three in a row. Sam Bennett had two assists, and Daniil Tarasov made 22 saves.
The two-time defending Stanley Cup champions would have been eliminated from Stanley Cup Playoff contention with a regulation loss.
Michael Amadio had a goal and an assist, and Drake Batherson and Jordan Spence scored for Ottawa (38-26-10), which has lost three straight. Linus Ullmark allowed five goals on 16 shots before being replaced by James Reimer, who made 12 saves in relief.
Noah Gregor made it 1-0 for the Panthers eight seconds into the first with the fastest goal to start a game in franchise history. After Florida won the opening face-off, Jones sent the puck into the offensive zone and off the end boards, where it caromed to the front of the net. Ullmark deferred playing it before it rolled off Spence’s stick and went right to Gregor for the finish.
Mackie Samoskevich made it 2-0 at 1:06 with a power-play goal, redirecting Jones’ backdoor pass.
The Panthers extended the lead to 3-0 with another power-play goal at 9:09. Verhaeghe gathered a loose puck to the right of the net and banked in a sharp-angled shot off Ullmark.
Florida then pushed the lead to 5-0 by scoring twice within 34 seconds. A.J. Greer one-timed a pass from Eetu Luostarinen at 14:02, and Verhaeghe scored on a 2-on-1 at 14:36, chasing Ullmark.
Batherson scored his 30th of the season to make it 5-1 at 1:40 of the second period, scoring with a wrist shot from the left face-off circle.
Tkachuk got his fourth point of the night, giving Florida a 6-1 lead at 12:41 when he charged the net and beat Reimer off a pass from Bennett.
Spence then cut it to 6-2 at 15:14 with a point shot through traffic, and Amadio made it 6-3 at 4:29 of the third period by one-timing a Ridly Greig backhand feed in the high slot.
The Senators had a great power-play chance after Gregor was assessed a five-minute major and match penalty for a check to the head of Carter Yakemchuk at 11:26 and Panthers defenseman Gustav Forsling was called for tripping at 15:22 to make it 5-on-3.
Ottawa then pulled Reimer for a 6-on-3 advantage but failed to score.
Yakemchuk left the game after the hit from Gregor and was helped to the dressing room.
Florida defensemen Dmitry Kulikov and Aaron Ekblad also left the game in the third. Kulikov was hit in the face by a deflected puck, and Ekblad, who tied Aleksander Barkov for the most games played in franchise history with 804, blocked a shot with his hand on the penalty kill.
