TAMPA -- Through four games of the Eastern Conference Final, we've seen some stretches when the Pittsburgh Penguins have played their best game and others -- maybe not as many -- when the Tampa Bay Lightning have been at their best.
So far, what we haven't seen is the Penguins and Lightning playing at their highest level at the same time.
With the best-of-7 series tied 2-2, Lightning coach Jon Cooper expects that to change beginning with Game 5 at Consol Energy Center on Sunday (8 p.m. ET; NBCSN, CBC, TVA Sports).
"The more games you add, the more of a roller-coaster ride it's going to be," Cooper said Saturday before the team's flight to Pittsburgh. "You have to understand that those Game 1 and 2s are the feel-out process, but I think a desperation level comes in at some point during the series."
After losing 3-1 in Game 1, the Penguins were the desperate team in Game 2 and pulled out a 3-2 victory in overtime. That appeared to carry over into Game 3 as the Penguins dominated in a 4-2 win that would have been more lopsided if not for the play of Lightning goaltender Andrei Vasilevskiy.
Video: Breaking down Game 3 of the Eastern Conference Final
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.
Video: PIT@TBL, Gm4: Vasilevskiy makes a strong stop in 1st
It also helped that Tampa Bay grabbed the lead 27 seconds into the game on Ryan Callahan's deflection goal.
"Whenever you score a goal in the first shift, that's great for your confidence and building momentum," forward Alex Killorn said. "I think we were playing a lot more of a physical game [Friday], really making their defense play defense instead of getting up the ice and playing offense. I think that wears on a team and, throughout a game, you can be more successful doing that."
While Penguins coach Mike Sullivan is debating whether to stick with rookie Matt Murray or turn to veteran Marc-Andre Fleury in net for Game 5, Cooper doesn't have a decision to make yet on his starting goalie.
Bishop, the Lightning's No. 1, has been out since sustaining a left leg injury in the first period of Game 1. Although Bishop returned to practice Thursday and was on the ice again for the morning skate Friday, he appeared limited in his movements and Cooper indicated Saturday the 2016 Vezina Trophy finalist had not been cleared medically to play.
When asked if it will be a difficult decision to go back to Bishop after Vasilevskiy has played well in his absence, Cooper replied, "That's a question you've got to ask when [Bishop] is cleared."
From the Lightning's perspective, it doesn't matter if the Penguins switch to Fleury.
Video: PIT@TBL, Gm4: Fleury stones Namestnikov on doorstep
"Doesn't change anything we do," Killorn said. "We faced him in the third period [of Game 4]. He's a good goalie. He's won a [Stanley] Cup. He's done a lot of good things. We can't worry too much about what they do with their goalie."
The focus for the Lightning has to be on how they play. For the first two periods on Friday, they played their best hockey of the series and looked like the team that defeated the Detroit Red Wings and New York Islanders in the first two rounds.
Expect the Penguins to elevate their play again Sunday, however, meaning two good periods probably won't be enough for the Lightning.
"[Friday] we definitely put a full game together," Lightning defenseman Jason Garrison said. "Obviously, we had a little bit of a lapse in the third, but that's the way we need to play for a full 60 [minutes] from here on out."