The Lightning never had a lead on Tuesday night, falling behind 1-0 in the first period on a redirected goal from Sam Bennett before Guentzel tied the score on the power play at 12:21 of the first.

Sam Reinhart gave the Panthers a 2-1 lead with 45 seconds remaining in the first on another deflection in front of goalie Andrei Vasilevskiy.

In the second, the Panthers picked up three goals in quick succession — two coming off the power play, both from Matthew Tkachuk — to give themselves a stranglehold on the game.

“Matthew is good on the power play, really good. He knows what he’s doing down there,” Cooper said. “We kind of gave him the second one when we threw it right on his stick. We’ve got to be better, we have a pretty darn good penalty kill and they went 3-for-3 (on the power play). That’s on us.”

But first came Nate Schmidt‘s goal at 4:41 of the second, the defenseman charging into the slot to clean up a loose puck in the crease.

Tampa Bay challenged for goalie interference but lost, giving the Panthers a power play chance.

“It only hurts if you get scored on,” Cooper said when asked about the lost challenge.

This one hurt.

Tkachuk scored a mere 14 seconds into that power play to give Florida a commanding 4-1 lead. He added his second power-play goal at 9:44 to make it 5-1.

“Our PK wasn’t as sharp tonight,” McDonagh said. “Missed some reads and give them credit, they capitalized. We’ve got another level that we can get to here and we’ve done it before. Our belief is there in our system, in the guys in the room, and handling adversity here. It’s playoff hockey and we know we’ve got to respond here now.”

Brayden Point got a goal back for the Lightning before the end of the second, but Schmidt’s second goal of the game 5:09 into the third period — Florida’s third power-play goal — put the Panthers back up by four.

“There are a lot of things we can improve on,” Tampa Bay captain Victor Hedman said. “We gave up 16 shots, and that’s usually a good night.”

It’s the fourth time in five seasons the Lightning are playing the Panthers in the playoffs. The previous three times, the winner went to the Stanley Cup Final.

“They’re a good team,” Hedman said. “They’ve got a lot of good players. For us, it’s all about refocusing, make sure we have a good practice tomorrow and get ready for the next one.”