Facing the possibility of being run out of the series if they continued to play the same way, the Lightning pushed back in Game 4 on Friday, jumping out to a 4-0 lead through two periods before holding on for a 4-3 victory.
It will be the Penguins' turn to respond in Game 5, but the Lightning know they can't afford to let up or they could be on the brink of elimination.
"They came into Game 3 and they had a little bit more want than we did in that game," Cooper said. "Now, you get to Game 4, our desperation level is as high as it can be, and we take Game 4. And, when you start peeling down a series, now you're down to a best-of-3 and, ultimately, now you're probably getting two desperate teams.
"So, I don't know if you're going to see anybody's 'B' game as we go forward here."
The Lightning didn't show many glimpses of their 'A' game in the first three games. They came closest in Game 1, when they were opportunistic in capitalizing on the Penguins' mistakes but relied heavily later in the game on Vasilevskiy, who made 25 saves after coming in to replace the injured Ben Bishop.
In the first two periods of Game 4, the Lightning played a lot more like they want to play - like they need to play - to defeat the Penguins. They got the puck out of their end and moved it up the ice quickly. That enabled them to put more pressure on the Penguins defensemen in the attack zone rather than spend extended shifts just trying to get the puck out of their own end.