A five-game winning streak was well within reach for the Penguins, holding onto a two-goal lead with 20 minutes to go tonight against the Islanders at PPG Paints Arena. But everything came crashing down for the Penguins, handing the Islanders a four-goal final frame to lose 4-2 and have their streak snapped at four games.

"We didn't push back hard enough," Mike Sullivan said of his team's effort. "We didn't play the right way. We beat ourselves in so many ways in the third period."

There were elements to like about the way the Penguins played in the first 40 minutes of the game. They were being outshot, 25-17, sure. But Tristan Jarry was again holding the Penguins in the game. Joona Koppanen scored on the Penguins' first shot to give them an early lead, and Sidney Crosby found the back of the net with 15 seconds left in first to double the lead. Both teams held each other of the scoresheet in the second. All the Penguins needed to do was get through the next 20 minutes without letting the Islanders get a pair.

Kris Letang lost the puck at the blue line seconds into the final frame, setting up Kyle Palmieri on a breakaway. Palmieri's initial shot hit the post, bounced into Jarry's back and rebounded into the net. 

"It just hit the extension and went inside," Letang said. "And I was taking the wall away. I tried to keep it in with my foot and it kicked right through the middle."

Sullivan said that the sequence that led to the Islanders' first goal was a result of "playing the game with not a whole lot of purpose," and that gave them life.

It was almost all Islanders the rest of the way. Noah Dobson tied the game just over five minutes later. The rush itself was hard to prevent -- it was just the result of a Crosby shot that went wide of the net and rimmed around the boards, but the Penguins made it easy from there. Conor Timmins slid to block an anticipated shot that didn't come and took himself out of the play, leaving Matt Grzelcyk alone to defend the net-front -- or rather, just watch Dobson score.

The go-ahead goal came with just under six minutes remaining. A failed Erik Karlsson pinch left Ryan Graves trailing Pierre Engall in a foot race for the loose puck, and Engvall's shot off the rush got past Jarry. The fourth goal was scored into an empty net as the Penguins were pushing for the tying goal.

"We give up that early goal, and after that you fall back on your heels," Letang said of the collapse. "We basically let them come at us."

Bryan Rust said he thought the Penguins were "playing well" in the first two periods, then fell flat in the third.

"We had a bunch of self-inflicted wounds," Rust said. "We didn't execute. Simple as that."

Crosby thought the Penguins lacked "pushback."

"We just beat ourselves," he said. "We made some mistakes. Obviously, they're going to push, it's 2-0. ... It's just one of those things where we started chasing a bit."

Nobody should have expected the Penguins' exceptional run they were on to continue for too long. As I explained after their win over the Devils, there was real data that was able to quantify that. The stat PDO aims to show things that could be explained as "puck luck" by adding a team's save percentage and shooting percentage -- anything above 1.00 suggests that a team has some luck involved and good play is getting propped up by an exceptionally high save percentage and/or shooting percentage, and anything under 1.00 suggests that a team is unlucky and is not getting that kind of help. In either direction, teams generally regress to the mean over time. In the Penguins' four-game winning streak, they had the highest PDO in the league by a wide margin at 1.145, getting help from a high shooting percentage of 21.43%.

In this game, that shooting percentage regressed to a more realistic 9%, slightly below league average. Had the Penguins been getting the kind of results in that department they were getting throughout the streak, maybe that's enough to overcome their own mistakes defensively. But at the same time, cleaning up the mistakes defensively would have made up for an average shooting percentage -- that's what good teams do, that's what would create a sustainable run.

The Penguins aren't making the playoffs. They aren't mathematically eliminated just yet, but the hole they've dug themselves into is just going to be too much to overcome. 

Being this far out of the race with no way out probably isn't the most conducive environment for playing the tightest, most responsible games defensively. But if the Penguins really do want to finish the season on a high, the place to start would be cleaning up their own mistakes.