It was one of the biggest topics on an otherwise quiet playoff off-day.

On Tuesday, with the Rangers trailing the Penguins 2-1 in the third period, forward Viktor Stalberg was whacked in the face by a high stick from Penguins defenseman Kris Letang, who was battling along the boards with Stalberg and Dominic Moore. Letang was not penalized and did not receive any supplemental discipline from the NHL on Wednesday.

Stalberg, who lost three teeth, spent Wednesday morning at the dentist, but teammates said they expected the Swedish winger to be fine for Game 4 at the Garden on Thursday.

Letang said the contact was unintentional. Nonetheless, NHL rules state that a referee can call minor or major penalties if players are not in control of their sticks and injure opponents.

Unless a suspension is handed out, the NHL doesn’t divulge its reasoning. A source said the league told the Rangers that there was no supplemental discipline because Letang was hit from behind by Moore and was off balance.

Rangers coach Alain Vigneault was annoyed but not publicly livid. “We might feel that it seems deliberate,” Vigneault said. “The NHL doesn’t see it that way and the referees on the ice didn’t see it that way, so you’ve just got to deal with it and focus on the next game. Frustration right now is not what we need . . . I think we need to focus on coming out with great execution. Our execution wasn’t good enough.”

Letang, who practiced at Madison Sqaure Garden on Wednesday, said that he “went in the corner trying to clear the puck when my stick was up, and I got hit at the same time I was going forward. Unfortunately, I hit him and he was bleeding. Not in a million years would I try to hit somebody in the face like that. When I was skating by the bench I said, ‘Sorry,’ but I didn’t even know if I hit him or if I hit Dominic [Moore] behind me. I got hit and I went off balance and I was leaning forward.”

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Penguins coach Mike Sullivan said he “wasn’t really concerned [about discipline from the league] because I didn’t think there was intent. The way we saw it, it was a hockey play. He got hit from behind, he was trying to grab ahold of his balance. It’s unfortunate that he got his stick up.”