The Rangers are being honest with their report Mats Zuccarello will be sidelined “indefinitely” in the wake of the injury the winger suffered last Friday.

But The Post has learned from several sources Zuccarello definitely will not be available for Round Two against the Capitals, which commences Thursday night at the Garden.

Beyond that, Zuccarello’s availability for a hypothetical Eastern Conference final, and indeed, the Stanley Cup final itself, is in doubt.

Zuccarello, the club’s first-line right wing, is suspected to have sustained a concussion when he was struck on the left side of the head by Ryan McDonagh’s drive at 15:30 of the first period of Game 5 against the Penguins. After the play, he skated slowly to the Rangers’ bench before heading to the locker room.

It is unknown whether the 27-year-old Norwegian, who was hospitalized for at least one night over the weekend, suffered additional damage.

Marty St. Louis will move into Zuccarello’s spot on the unit with center Derick Brassard and left wing Rick Nash, thus reforming the line that was intact for eight games in November.

“I think they play similar; they have the same height,” a chuckling Brassard said of the diminutive wingers. “They both like to make plays and like to work off [their linemates].

“We had some good games together. If we want to move on, our line has to be really good.”