Alexander Romanov had shoulder surgery and is expected to be out 5-6 months, the New York Islanders announced Sunday.

The 25-year-old defenseman was injured late in a 3-2 win against the Dallas Stars on Nov. 18 when he was boarded behind the net at 19:32 of the third period by Stars forward Mikko Rantanen, who was also given a game misconduct.

“First of all, he’s not happy; there’s no doubt about it,” Islanders coach Patrick Roy said before their game against the Seattle Kraken (5 p.m. ET; KHN/Prime, MSGSN, KONG, SNP, SNW). “… We have to move on, and you don’t replace a player like him. You hope that the guys coming in will fit in, and hopefully that [Adam] Boqvist will play like he’s been playing.

“So, I mean, it’s an opportunity for [Boqvist], and he needs to take advantage of it. We’ll see what (GM Mathieu) Darche decides, but we have Marshall [Warren] that played really well for us and we’re comfortable to have him playing if he has to.”

Romanov has one assist and 31 blocked shots in 15 games this season and is averaging 19:27 of ice time. He was placed on injured reserve Wednesday.

“Obviously, I never meant to do that,” Rantanen said Wednesday. “I’ve never done that my whole career. I play hard, but I never try to be dirty on purpose. I think I got clipped a little bit, and then he [fell] forward. Unfortunate moment, but I never really meant to do it. Hopefully he’s not too bad.”

Rantanen was automatically suspended one game Sunday for receiving another game misconduct when he boarded forward Matt Coronato in the second period of a 3-2 shootout loss at the Calgary Flames on Saturday.

NHL.com independent correspondent Stefen Rosner contributed to this report