With Oliver Wahlstrom unavailable for Game 6 Wednesday night at Nassau Coliseum, Travis Zajac slotted right in and had a hand in helping the Islanders to a 5-3 series-clinching win over the Penguins.

Zajac, who the Isles acquired from the Devils at the trade deadline along with Kyle Palmieri, had been a healthy scratch this entire first-round series until Game 6 and hadn’t seen game action since May 8.

The former longtime Devil won the offensive-zone faceoff that led to Ryan Pulock’s goal at 8:48 of the second period, which gave the Islanders their first lead of the night at 4-3. He also saved a goal at the end of the first period, swiping away a loose puck that was going to trickle in.

Since joining the Isles in April, Zajac has been scratched nine times. But Trotz has maintained the 36-year-old Zajac has been patiently waiting for the call.

“It’s difficult,” Zajac said after the win. “You want to be out there on the frontlines with your teammates badly, being part of the wins and the losses and the ups and downs. But, like I told Barry, I’m here for the long haul. I’m here to help any way I can, be a part of it any way I can.

“Like everybody else when their name is called, you got to go in and do the right things and play winning hockey and control what you can control.”

Wahlstrom was not on the ice for morning skate after leaving Game 5 in the third period following a collision with Penguins defenseman Mike Matheson that caused him to fall awkwardly on his right leg. Trotz classified the 20-year-old as day-to-day and he was considered a game-time decision, but ultimately didn’t play.

“It makes it easier on everybody,” Trotz said of how Zajac has handled his new role. “One of the things that you want, is good people. You’re not going to find a better person than Travis. As I said when I had to tell Travis he wasn’t dressing for the first time in probably 1,000 games, I mean, that’s probably a harder conversation. But he just said, ‘Hey, coach, I’m good.’ I know it probably hurt the first time, but I think I said, ‘I have a lot of loyalty and I have a lot of trust in that group that I’ve had. This is where we want to go tonight or whatever, you’ll be a part of it at some point.’

“He’s said, ‘I’ll be ready whenever you want me to play.’ That’s just Travis Zajac. That’s why he was a captain and that’s why he’s played so long in the league.”

The Isles’ top defensive pairing of Adam Pelech and Pulock showed just how much they’ve grown since the last time they faced the Penguins in the playoffs in 2019.

In a team-high 98:48 of ice time through six games, the duo allowed just three goals while facing a steady diet of the Penguins’ top line in Jake Guentzel, Sidney Crosby and Bryan Rust.

“Before, when I tried to do it too early for them, it was a little bit too much for them,” Trotz said. “As we kept, I would say force feeding them and giving them those type of matchups, they got a comfort level and they’ve become a really good, really good pairing in the National Hockey League.”

Trotz revealed that Michael Dal Colle “tweaked something” the other day and was unavailable Wednesday night.