In a best-of-series, there’s a certain margin of error afforded each team. It’s exactly three games. After that, a team has to be perfect to get through to the next round.

After Mark Stone’s game-winning goal in overtime won Game 5 for Vegas, Colorado’s margin for error is now completely gone.

Once up 2-0 in this series, the Avalanche has seen that lead evaporate and now is just one loss away from their third consecutive second-round exit.

Up 2-0 was how Colorado went into the third period, too, after pacing the majority of play through the game’s first 40 minutes and getting goals from Brandon Saad and Joonas Donskoi.

That two-goal lead lasted just over three minutes into the third period as Vegas struck twice on bad Colorado turnovers and got the score to even. Each team had their chances in the third period but for the second time in the series, overtime was needed.

It was nearly not much overtime as J.T. Compher had one of the game’s best looks on a juicy rebound just 10 seconds into the extra frame but Compher’s shot was back into Marc-Andre Fleury’s body and stopped. Just moments later, two blocked Ryan Graves shot attempts turned into a breakaway for Stone, who scored his first goal of the series give Vegas the 3-2 advantage in the series.

It was a gut-wrenching loss for the Avalanche because they played a great hockey game but still lost. After what felt like three complete games of watching Vegas work them over, the Avs finally punched back in a meaningful way.

A 2-0 lead into the third period but couldn’t out how to close. A turnover from Andre Burakovsky in his own zone turned into an Alex Tuch goal and just minutes later a turnover on a four-player Avalanche rush up the ice was turned over and became an odd-man rush the other way. Jonathan Marchessault scored his fifth goal in the last three games and just like that it was tied.

“I didn’t have a problem with the way we played the third period,” head coach Jared Bednar said. “I had a problem with the way we managed those two situations, right?”

A third mistake, the Graves shot attempts blocked and kicked out to create the Stone game-winning goal were Colorado’s most egregious blunders and Vegas capitalized on all three in a way the Avalanche failed to do on the other end.

“You’ve got to work through mistakes,” Bednar said. “That’s what it is. It’s a game of mistakes.”

Seeing the Vegas captain streaking down the ice and making the game-winning play only emphasized Colorado’s own star player’s notable struggles once again tonight. This was the third straight game Nathan MacKinnon failed to register a point and since the 7-1 blowout in Game 1, he has just one assist.

It’s no accident Colorado has struggled to put Vegas away as they’ve blown two third-period leads in Games 3 and Game 5 with MacKinnon not finding the scoresheet at all.

The NHL is a league that usually rewards the team that can get to the third goal. Colorado failed to do it in Games 3 and 5 and lost both in late, heartbreaking fashion.

Instead, the Avs find themselves staring down the barrel of their mortality and on the verge of potentially significant changes in the offseason as they face the oncoming sting of the inevitable salary cap crunch.

“We don’t have much time to do anything but rebound and forget about this one and move on,” Gabe Landeskog said. “We’ve got to go into Vegas and win a hockey game.”

Or else.