The Islanders’ fourth line set such a high standard this regular season, with Matt Martin, Casey Cizikas and Cal Clutterbuck combining for 33 goals, that seeing them go pointless through the opening two games of this first-round series seemed to leave one thinking they hadn’t played up to par.

Their main goal, especially in the postseason, is to contribute any way those three Islanders can, usually by leaving a mark or two on opponents. Martin, Cizikas and Clutterbuck were doing that early in Game 3, but having a bit of trouble staying on the legal side of the fine line each of them walks this time of year.

“We’re just trying to play our game,” Cizikas said Sunday morning. “Obviously, I think we can be better in some areas, but it’s really just a matter of keeping it simple. Just be tough out there, try to finish your checks but keep your emotions under control.”

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Each of the three took a costly minor in the first two periods of a wild Game 3, not the sort of contributions the fourth line wants to make. On a delayed penalty call in the first period, Clutterbuck got his stick up on Dmitri Kulikov to negate the power play. Martin took a nitpicky minor for roughing with 1:02 left in the first, and the Panthers scored 13 seconds after Martin exited the penalty box in the second.

Cizikas lost a key draw late in the second and was sent off for tripping red-hot Reilly Smith, a minor that carried over into the third.

Through the first two games, the Cizikas line ended up on the ice often against the Panthers defense pair of Kulikov and Aaron Ekblad, so Clutterbuck and Cizikas took every opportunity to give Ekblad, the talented young Panthers defenseman, a face wash or extra shove after every whistle.

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Cizikas even delivered a below-the-belt punch to Ekblad in Game 2 that drew an extra minor. “Just playoff hockey,” Ekblad said. “We’re trying to play good, tough playoff hockey.”

Martin led the NHL in hits for a fifth straight season at 365, and that’s been more what he and his linemates have been known for the past two seasons. But timely goals, including 15 from Clutterbuck, became a hallmark for the only line Jack Capuano kept together from the season opener to the end of the regular season.

In the postseason, everyone ratchets up his physical game, so it was incumbent upon the Cizikas line not to step over the line, especially in the first playoff game in Barclays Center and the sellout, towel-waving crowd that turned out Sunday night.

“Coming home, with all the atmosphere we know we’re going to have and the hatred that’s starting to build this series, there’s a need to be relaxed, to be disciplined and understand we’re here to win games,” Martin said. “You have to be hard to play against but you also have to be disciplined if you want to help the team.”

Martin did draw a cross-checking penalty on Alex Petrovic in the second period Sunday, only a few seconds after he nearly swept a rebound past Roberto Luongo. The Islanders scored on a five-on-three soon after, so it wasn’t all bad news for the Isles’ well-known line.

“You have to play smart,” Cizikas said. “You take your hits when you can and make sure you’re not going out of position to make a hit and keep it as simple as you can.”