He was disappointed, in himself, in the situation, in the result, as Frank Vatrano scored off a face-off on the power play to tie the game 1-1.
And yet, Stamkos was calm.
"It was weird," he said. "I mean, it's easy to say now, but I wasn't as rattled as I usually am in those situations. I think I was just confident in our group that we'd find a way, whether it was in regulation or was in overtime. We deserved to win the game tonight."
RELATED: [Complete Rangers vs. Lightning series coverage]
He returned to the ice, for a face-off and a new start and a chance. And then it all happened, so fast. There was Ondrej Palat with the pass that sprung Nikita Kucherov. There was Stamkos coming down the ice, getting ahead of Rangers defenseman Jacob Trouba, putting him in just the position to take the Kucherov feed and make the shot, the puck bouncing off goalie Igor Shesterkin and then off Stamkos's leg and in.
There he was, the captain and the leader answering for his own sins, scoring 21 seconds after Vatrano had tied it. There was 6:32 remaining and Stamkos, with his second goal of the game, was willing the Lightning into their third straight Stanley Cup Final.
That's where it would end, with a 2-1 win Saturday at Amalie Arena in Game 6 of the best-of-7 series, with each goal coming from Stamkos, who has always been the team's north star.
It was fitting.
"In an elimination game, to not only score the first but to answer back 21 seconds after they [score], it's like, you're so proud," coach Jon Cooper said. "And you're proud that 'Stammer' got to do it. He'll be the first one to push the accolades to everybody else, but he had a [heck] of a series, and I think it paid off in Game 6. Just happy for him and his legacy as the captain of this team."