TAMPA -- The Tampa Bay Lightning gave up six goals in the first two periods of a 7-4 loss to the Ottawa Senators at Amalie Arena on Tuesday.
The Lightning (48-18-4) lost in regulation for the first time since Feb. 17 and their Atlantic Division lead over the Boston Bruins dropped to four points having played two more games.
"I don't know. Turnovers, bad tracks, inability to block shots, inability to kill a penalty. Add them all up," Tampa Bay coach Jon Cooper said. "Probably a little bit of bad bounces, I guess, but maybe that drops it by one or two. Still score four and lose by three … that's a tough night at home."
[WATCH: All Senators vs. Lightning highlights]
Mike Hoffman scored twice for the Senators (25-33-11), who won consecutive games for the first time since Feb. 15 and 17. Mike Condon made 42 saves.
Ottawa, next to last in the Eastern Conference, defeated the Florida Panthers 5-3 on Monday.
Video: OTT@TBL: Hoffman hustles for second of the game
"I think we knew going in to this game we were going to have to play at our absolute best and get some puck luck with us to have a chance to win the game, and I think that's what happened," Senators captain Erik Karlsson said. "At the end of the day, we are still playing to win all the games moving forward, trying to feel as good as possible about our game and ourselves, and as of lately we have done a good job of that."
J.T. Miller scored his first NHL hat trick, and Ryan McDonagh scored his first goal since being traded to the Lightning. Andrei Vasilevskiy, who would have set a Tampa Bay single-season record with his 41st win, was pulled after the second period.
"This isn't really a night to take personal success," Miller said. "Not after a game like that. We have things as a group to work on and that's what we're going to stay focused on."
Video: Dunkin Donuts Breakaways: Paajarvi scores on rebound
Miller gave the Lightning a 1-0 lead at 4:19 of the first period. Magnus Paajarvi tied it 1-1 at 7:47, Ryan Dzingel gave the Senators a 2-1 lead with a power-play goal at 10:47, and Pyatt pushed the lead to 3-1 at 11:24.
"It's a good sign to see when these guys are going, when everyone is working, everyone is pulling their own weight," Condon said. "I never doubt the offensive skill in this room. So it was great to see."
Miller made it 3-2 with a power-play goal at 2:03 of second period. Gaborik responded with a power-play goal at 7:18 to give the Senators a 4-2 lead.
Hoffman increased Ottawa's lead to 5-2 at 13:44 with his 20th goal of the season. Miller scored his second power-play goal at 16:26 to make it 5-3.
Video: OTT@TBL: Dzingel picks the corner for nice PPG
"Each season that's what I expect myself to do, that's why I'm on this team, to put pucks in the net," Hoffman said. "Tonight, to get a few, they are a powerhouse team and we needed to get a few more than that and it was nice to come out on top."
Karlsson made it 6-3 at 18:30, and Hoffman extended the lead to 7-3 at 3:46 of the third period.
McDonagh scored at 12:44 to make it 7-4.
Nikita Kucherov and Steven Stamkos each had three assists for Tampa Bay. Kucherov leads the NHL with 91 points (34 goals, 57 assists).
Goal of the game
Hoffman's goal at 13:44 of the second period.
Video: OTT@TBL: Hoffman cashes in on big rebound in front
Save of the game
Condon's save on Stamkos at 1:23 of the second period.
Video: OTT@TBL: Condon shuts the door on Stamkos, Miller
Highlight of the game
Miller's goal at 16:26 of the second period.
Video: OTT@TBL: Miller buries Stamkos' feed for hat trick
They said it
"We are not playing into our structure defensively and taking care of the puck in areas of the ice where there could be potential danger. It's unacceptable. It's hard to win games giving up that many goals. It's hard to do it." -- Lightning defenseman Anton Stralman
"The guys paid the price to the very, very end. It was a really good team effort. You come on the road and the two best teams in the League lately and we beat them both. So I think the players have shown again that they keep going, we want to win games, and they keep improving." -- Senators coach Guy Boucher
Need to know
Peter Budaj relieved Vasilevskiy and made three saves on four shots in his first NHL game since Dec. 29. … Hoffman has scored at least 20 goals the past four seasons. … Kucherov is the fifth Lightning player to score at least 90 points in a season. ... Seven goals were the most for Ottawa since a 7-4 win against the Arizona Coyotes on Oct. 18, 2016. ... The Lightning last gave up seven goals in the regular season Jan. 12, 2015, a 7-3 loss to the Philadelphia Flyers. ... Miller has nine points (five goals, four assists) in seven games since he and McDonagh were traded by the New York Rangers on Feb. 26.
Senators: Host the Dallas Stars on Friday (7:30 p.m. ET; TSN5, RDS, FS-SW+, NHL.TV)
Lightning: Host the Boston Bruins on Saturday (7 p.m. ET; SUN, NESN, NHL.TV)
Video: Hoffman, Condon strong as Senators top Lightning, 7-4