Maxim Tsyplakov, right, celebrates his third period goal against the...

Maxim Tsyplakov, right, celebrates his third period goal against the Florida Panthers with Islanders teammate Marc Gatcomb at UBS Arena on Sunday. Credit: Jim McIsaac

PITTSBURGH — This is not a soppy reminiscence of the Islanders’ long-running but now defunct “Identity Line” with current third-line center Casey Cizikas between current TV star Cal Clutterbuck and the now never-used Matt Martin. But this is an acknowledgment — a reminder made crystal-clear by their last game — of how important a gritty, effective fourth line is for the team’s success.

The Islanders will enter Tuesday night’s game against the Penguins at PPG Paints Arena four points out of the Eastern Conference’s second wild-card spot. And it was their fourth line of Kyle MacLean centering rookies Maxim Tsyplakov and Marc Gatcomb — both of whom scored in a four-goal third period — that played a large part in the Islanders keeping their long-shot playoff hopes alive in Sunday night’s 4-2 comeback win over the Panthers at UBS Arena.

It also was a stark reminder that, for a major portion of this inconsistent season, coach Patrick Roy has not been able to count on that kind of contribution from whichever trio he’s used as a fourth line.

MacLean (three goals, five assists, 65 games) has been the constant and it’s been a season-long struggle for the second-year player, who has not built on the promise of the four goals and five assists in 32 games he had last year as a midseason call-up.

Gatcomb almost exclusively has been MacLean’s running partner since he was recalled from AHL Bridgeport on Jan. 14 (Martin last dressed for a game on Jan. 16).

Tsyplakov, with eight goals and 20 assists in 61 games after notching his first goal in 27 games, has been used up and down the lineup and, ideally if producing, is a top-nine forward. But his physical presence is a plus on a fourth line.

In their seasons together, Martin-Cizikas-Clutterbuck routinely set the tone by being on the ice to start the game and then quickly establishing a hard forecheck.

Roy started the game with his fourth line on Sunday, but that has been a rarity this season and was done only because he was matching the Panthers’ fourth line.

“That’s what it was in the past,” Roy said. “What I like is to match more. Offense against offense. I like to create offense against offense. The mentality is just different.”

That’s fine, especially given that Roy has not consistently entrusted his fourth line with the 12 or 13 minutes the Identity Line routinely received.

But any team is better when the coach can roll four lines. And the effort in skating and forechecking shown on Sunday by Tsyplakov-MacLean-Gatcomb allowed Roy to do that from the first period, when the Islanders outshot the Panthers 12-1.

“I thought we played a good first, second and third period,” said Gatcomb, who has four goals and an assist in 23 games. “The third period we got some more bounces. We had our chances all night. It was good to finally see them go in.”

The line combined for six of the Islanders’ 34 shots. Its analytics were superb, with NaturalStatTrick.com reporting the trio had a 12-3 advantage in chances created skating five-on-five while compiling a team-best Corsi For percentage of 80.0.

“That gave us that energy that we needed,” Roy said.

The Islanders would be so much better off, for the rest of this season and next, if they could get that kind of fourth-line production consistently.