Mike Ribeiro plays the hero with the game-winning goal in overtime that gives the Capitals a dramatic 2-1 victory in Friday night’s Game 5. (Video by Travis Swain for Synthesis/Koubaroulis LLC./The Washington Post)

Very little can replicate the tension and tumultuousness of the third period or overtime of an NHL playoff game, when each player skates with the knowledge that one fumbled puck can change the series and the season. Make a play, be a hero. Botch a play, live in infamy. The line is thin, the stakes are high and it’s all repeated, night after night.

“You think about it,” Washington Capitals defenseman Karl Alzner said Saturday. “You don’t want to be that guy.”

Given the way the Capitals and New York Rangers have played this Eastern Conference quarterfinal series, there’s every reason to believe Sunday’s Game 6 — in which the Capitals could advance or the Rangers could survive — will come down to such an eye-blink of an instance. Friday night, New York center Derick Brassard couldn’t clear a puck out of his own end, and Rangers defenseman John Moore couldn’t get his body between Washington center Mike Ribeiro and the goal. Thus, the difference: Ribeiro’s overtime winner that put the Capitals up three games to two.

The Rangers’ job: Forget that. The Capitals’ job: Capitalize on it. Given the feel of this series, the recent history of these two teams and the nature of the Stanley Cup playoffs, something very similar — one play made or not made, one rebound cleared or kept in the zone — could turn Game 6.

“It’s kind of situation where you can make a mistake, and a mistake can cost you a goal and cost you a series,” said Capitals star Alex Ovechkin. “It’s not like regular season, 82 games.”

This is, indeed, nothing like the regular season. The last four games of this series have been decided by a single goal. (The one blowout? The Capitals’ 3-1 victory in Game 1.) That fits into the narrative for these teams. Last year, when they faced each other in the Eastern Conference semifinals, the final six games were decided by one goal. Two went to overtime.

Remember the Capitals’ seven-game victory over Boston in the first round as excruciating? Each game was decided by one goal, and four went to overtime. In fact, since the Ovechkin-era Capitals began going to the playoffs in 2008, 39 of their 56 postseason games — nearly 70 percent — have been decided by one goal.

Such tension has an impact on the crowd, which has no idea if there will be hockey for another two minutes or another two hours. But it also impacts the players, even if they’re familiar with such circumstances.

“You find yourself more mentally tired after the game than you do during the regular season,” Capitals forward Jason Chimera said.

The two overtime games thus far in this series have ended relatively quickly — Mike Green winning Game 2 eight minutes into the extra session, then Ribeiro just before the halfway point of the first overtime period in Game 5. Ideally, the Capitals would like to finish the Rangers in regulation on Sunday.

But if they can’t, they won’t be alone. Through Friday night, 14 of the 48 first-round playoff games across eight series — almost 30 percent — had gone to overtime. Twenty-three of those games had been decided by one goal.

“You want to finish it off in the third period, because you get exhausted, and your legs can stop moving,” Ovechkin said. “You get hurt all the time in overtime. People are just exhausted. It’s hard to recover. If you play a minute and a half or a minute, go back and forth, you go back to the bench, and you’re just tired.”

That can lead to the unforgivable: A mental lapse, because when the legs go, the mind can follow.

“The hardest thing is to stay focused in overtime,” Ribeiro said. “You see the time going down. Chances are going up and down [the ice]. It’s really hard to stay composed and not freak out when you have the puck. You have to keep it simple at that time.”

Keeping it simple, though, might mean not pushing for a scoring opportunity. There is, then, a balance, one that the Capitals have discussed. The system installed by first-year Coach Adam Oates, in fact, deals with such situations: If players are to take risks, they’re not in risky areas of the ice.

“Hopefully, the way we play allows good things to unfold in the right places,” Oates said. “You’re not trying to make some miracle play in an area that we would never do at any time of the game. We chip the puck, we put it in a certain situation. [If] it goes off a guy’s knee incorrectly, we’re still safe.”

Safety will be a key in Game 6. But evaluating what is safe and what isn’t can be difficult, too. Oates, for one, believes there are more icing calls late in playoff games because players are simply desperate to clear the puck from their own zone — even if it means creating a faceoff back in that zone again. One of Oates’s assistants, Calle Johansson, has discussed with the defensemen that in these tight playoff games, no decisions can be made halfway.

“When you start to push, and you see a play, you’ve got to go for it,” Alzner said. “. . . Trust your read. If you’re going to make the right read, you should go all-in.”

They will be all-in Sunday night, with a chance to end the series, even if by a scant margin. Ten times in the last five years the Capitals have earned a chance to win the next game and advance to the next round. They have won only three of those games. Yet here they will be late Sunday afternoon, with the tension back, tiptoeing up to that line between making a play, and making a mistake.

“You can’t live in fear,” Chimera said. “You’ve got to try to make some plays.”