The Lightning were 0-for-6 on the power play, including a 5-on-3 for 1:34 late in the first period.
"Huge kill," Quenneville said. "You give that team a 5-on-3, hopefully you kill it most of the time because they're going to find an empty space. Obviously with [Nikita] Kucherov ... it would've definitely almost been impossible to get through it. So we got a break there."
The Lightning struggled on the power play without Kucherov, a forward who is out indefinitely with a lower-body injury.
"Obviously we're missing 'Kuch,' one of the best half-wall guys in the game," Point said. "Our power play runs through him. It's going to be a work in progress. There's going to be things we have to iron out, but tonight wasn't good."
Barkov gave the Panthers a 2-1 lead at 3:40 of the third period when he scored off a loose puck off the stick of Carter Verhaeghe.
"Any goal is huge, obviously we scored some goals," Barkov said. "But they tied the game up, and when we scored right away it was like we never lost the lead."