PITTSBURGH – As Mike Sullivan returned to Pittsburgh for the first time since he and the Penguins organization parted ways last April, the new Rangers coach had a more immediate problem than controlling whatever emotions he was dealing with in coming back to PPG Paints Arena.

He was coming back to Pittsburgh to face a team that had shut the Rangers out in their season opener Tuesday at the Garden. And he was doing it without his first-line center, Vincent Trocheck, whom the team announced Saturday will be out for an extended period with an upper-body injury.

Trocheck, a Pittsburgh native, left Thursday’s road win over Buffalo in the second period, and the Rangers said Saturday he will be out on a week-to-week basis.

“It sucks,’’ Rangers captain J.T. Miller said at Saturday’s morning skate of losing Trocheck. “He’s such a big part of the team. He’s a leader for the team, plays in all situations, but just his presence, being around, is… I mean, it’s only been half a day and it’s already it’s a crappy feeling. I know what he means to this group, and especially, not just his play, but his presence in the room.’’

“He’s a tough guy to replace,’’ Sullivan said of Trocheck. “He’s an extremely talented guy (who) plays in a lot of key situations for us, (is) one of our best center icemen in the faceoff circle, and obviously plays in every situation, the power play, the penalty kill, and is part of our top six (forwards). So those guys aren’t easy to replace.’’

With Trocheck out, Juuso Parssinen, who had been a healthy scratch the first two games, entered the lineup, and Sullivan had to move some pieces around. Mika Zibanejad, who has been playing right wing on Miller’s line, with Will Cuylle, shifted back to his natural center position and took Trocheck’s regular spot between wingers Artemi Panarin and Alexis Lafreniere. Conor Sheary, who had been playing on the third line, moved up to take Zibanejad’s spot on Miller’s line, and Parssinen, normally a center, played in Sheary’s spot at left wing on the third line, with rookie Noah Laba and right wing Taylor Raddysh.

Sullivan, when asked why he broke up the Miller-Zibanejad duo to move Zibanejad to center, said: “I think we need balance, and we need to give some of our other offensive people a center iceman that can think the game at their level and give them an opportunity to set them up for success.’’

As for returning to Pittsburgh, where he coached for 10-plus years and led the Penguins to back-to-back Stanley Cup championships in 2016 and 2017, Sullivan admitted it was an odd experience.

“Yeah, it’s a lot different, obviously,’’ he said of entering the arena as the visiting coach. “Being on the opposite side, it’s not something that I’ve given a whole lot of thought to, quite honestly, but I’m obviously so grateful for the opportunity that I had here to coach the Penguins for the amount of time that I was able to do it. We had a lot of good memories, and I’m grateful for that.’’

Sullivan was asked at the morning skate if he was happier to get his return to Pittsburgh out of the way early, as opposed to waiting.

“When I saw the schedule in the summertime, I was hoping we didn’t see (Pittsburgh) till March,’’ he said. “But it is what it is. It’s something that I can’t control. It’s an inevitability, and it’s just part of the process. So when the puck drops tonight, it’s going to be a hockey game (and) we’re going to do everything we can to try to win it.’’

Since the Rangers already played Pittsburgh in their season opener – and lost, 3-0 – Sullivan was asked what he may have learned from that game that would help him Saturday. He chalked up that result as a product of opening night jitters, plus the fact that Miller and Panarin were less than their best because they’d missed much of the preseason with injuries.

“They’re important guys for us, and with each game that they play, I think they’re going to get that much better,’’ he said.

Colin Stephenson

Colin Stephenson covers the Rangers for Newsday. He has spent more than two decades covering the NHL and just about every sports team in the New York metropolitan area.