Despite the missed opportunities, the game appeared destined for overtime until Colton's stunning goal.
Even after Lightning defenseman Jan Rutta carried the puck in following a turnover in the neutral zone by MacKenzie Weegar with 15 seconds left, the Panthers had two chances to clear the puck.
First, defenseman Gustav Forsling couldn't get it past Kucherov along the right-wing boards. Then, Luostarinen lost the puck when he had a chance to clear it near the blue line, allowing Ondrej Palat to keep it in at the right point and send it in deep.
"We've just got to get the puck out," Luostarinen said. "That can't happen there."
With the clock winding down, Kucherov retrieved the puck behind the net with Forsling chasing him from behind. But Weegar also decided to chip down from the opposite side of the net, leaving Colton unguarded below the left circle.
Having taken a quick peek over his left shoulder, Kucherov saw Colton skating in alone and made a deft backhand pass in front.
"He's got eyes in the back of his head, as you can see, because I didn't even know that he knew I was there," Colton said. "He gift wrapped it for me."
With the puck a bit on edge, Colton snapped Kucherov's pass over the right shoulder of Sergei Bobrovsky, leaving the Panthers in disbelief and silencing the crowd at FLA Live Arena.
"It's kind of tough," Bobrovsky said. "[Kucherov] was behind the net, right? Straight behind. So he make a good pass and it was a good shot."
It was another costly playoff lesson for the Panthers, who won the Presidents' Trophy as the NHL team with the best regular-season record but are still trying to figure out how to win in the playoffs against the Lightning.
"I loved our game," Brunette said. "I thought we were in a great position. Controlled the puck with 20 seconds left and just didn't manage it. Kind of made a fatal mistake."
Whether it proves fatal for the Panthers' season remains to be seen, but they now face a familiar situation they hoped to avoid repeating.
In the first round last season, Tampa Bay won the first two games of the series on the road before going on to eliminate Florida in six games.
"[The locker room] was quiet, but all the guys are pro," Bobrovsky said. "Everybody understands that next game is big. We can make a difference in the future, not in the past, and that's it. So we have to stay together again and keep working."