The Tampa Bay forward scored 2:06 into double OT on a play the Montreal Canadiens claim was offside as the Lightning won 2-1 in the opening game of their second round NHL playoff series on Friday night.
Game 2 of the best-of-seven series goes Sunday night at Bell Centre.
The Lightning were outshot 44-35 and got some breaks when Montreal's David Desharnais and Max Pacioretty hit posts early on behind shaky goalie Ben Bishop, but they found a way to pull out the win.
"It's nice but it doesn't mean much," said Bishop. "We just came off a series (against Detroit) where we lost the first game.
"You've got to put it in the past pretty quick. It's nice to win the first game but now we have to forget about it and get ready for the next one."
Tyler Johnson scored his league-leading seventh of the playoffs for Tampa Bay in the third period only to see Pacioretty tie it with 5:13 left in regulation to force overtime.
Replays showed the Lightning were clearly offside on the play that led to the winner, but it took 12 seconds from then until Kucherov scored, plenty of time to get the puck out of the zone. But defenceman Greg Pateryn coughed up the puck in a corner and Valtteri Filppula fed Kucherov in the slot for a quick wrist shot past Carey Price.
Montreal coach Michel Therrien seemed as upset at the linemen as at losing the opener.
"It's really frustrating, losing a game on an offside," said Therrien. "Those things are not supposed to happen.
"I thought our players had a great effort tonight. I couldn't ask for more. But to lose a game on an offside, it's not like a penalty. It's not a judgement call. It's black or white. It was clearly offside and we ended up losing the game."
A call went in his favour 2:56 into the first OT when a puck hopped over Jeff Petry's stick, sending Kucherov in on a breakaway. His shot was stopped and he pushed Price and the puck into the net with his stick. After review, it was disallowed due to preventing the goalie from making the save.
"I'm not going to complain about it. I don't think about it," Kucherov said.
He made good on it in the second OT.
"Boyle made a good play and Filppula got it through the D's legs. He put it right in my wheelhouse. I just had to shoot," Kucherov said.
The Lightning owned Montreal in the regular season, winning all five meetings, but the Canadiens, buoyed by a packed Bell Centre, stormed out of the gate only to waste their best chances to put Tampa Bay in a hole.
Bishop was clearly nervous, misplaying pucks around the crease, but then was able to settle down. He made the save of the night late in the second period when he stacked the pads and got a glove on Tomas Plekanec's shot from a short-handed 2 on 1 with Pacioretty.
The Lightning still had pressure after a power play and then got a break when Matt Carle's shot from the left point deflected off Johnson's skate past a helpless Price 2:34 into the third.
Pacioretty tied it at 14:47 on a wrist shot off the rush down the left side that Bishop caught, but couldn't squeeze with his glove. The puck dropped behind him into the net.
"I thought it popped up, then I don't know if it rolled down my back or what," said Bishop. "It was kind of right by my ear. I kind of took my eyes off it the last second and that's what happens."
Bolts captain Steven Stamkos appeared to jam a wrist in traffic near the Montreal net in the first period. He stayed in the game, but it will be something to watch for as the series progresses.
Notes — The Canadiens asked fans to dress and most did, filling the seats with red, white and blue. . . Montreal made no lineup changes. . . Forward J.T. Brown returned to the Bolts lineup, bumping Nikita Nesterov.