EAST RUTHERFORD, N.J. — In a season already full of demoralizing losses, the Nets were dealt yet another blow Monday morning when it was discovered that Rondae Hollis-Jefferson had fractured his right ankle in practice and will require surgery.

Hollis-Jefferson seemed jovial during the open portion of practice, laughing with coach Lionel Hollins, but the rookie swingman quickly got serious when it came to talking about the injury.

X-rays of the ankle had come back negative Sunday night, he said, but a CT scan Monday revealed the extent of the damage: a non-displaced fracture of the posterior talus.

He wore a hard plastic cast on the leg, and two long metal crutches were stationed nearby.

“I was stunned,” he said, adding that he suffered the injury while guarding Bojan Bogdanovic on Saturday. “I was hurt. It’s hurtful to be in that situation, trying to be one of the best rookies, working really hard, and then you get news like that . . . You don’t really know what to say. I’m lost for words.”

He’s out indefinitely, and a statement released by the team said no timetable will be established until he’s had the surgery. Hollis-Jefferson said he doesn’t know when the team will schedule the procedure but that he believes it will be in the next few days.

The injury originally was ruled a sprain, but Hollis-Jefferson realized that it probably was more serious. “It was a real bad roll,” he said. “This was different than most sprains that I’ve had in the past.”

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Hollis-Jefferson is averaging 5.2 points, and his average of 6.1 rebounds is fourth among rookies. He’s played 19 games, averaging 22.1 minutes, and helped anchor the Nets’ defense.

Hollins said he can’t predict how Hollis-Jefferson’s absence will affect a team that already is struggling to finish games and hold on to leads.

“I don’t know” if the Nets will miss Hollis-Jefferson’s defense, he said. “ predict whether we’re going to be worse or better because he’s out. There’s times when he was here and he wasn’t playing that we were good on defense . . . We’re going to miss his physicality, his size — 6-7 — his ability to go get rebounds, get hands on the ball.

“But how much, how bad? We’ll have to see as we go along.”

Until then, Bogdanovic likely will take Hollis-Jefferson’s spot in the starting lineup. Markel Brown and Wayne Ellington also are options off the bench. The team also can go to Shane Larkin, Hollins said.

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“He’s a young guy trying to play, and all of a sudden, his season is short-circuited for a bit,” Hollins said. “It’s tough when you get hurt any time, but especially when you’ve got to sit out for a long stretch . . . It’s just disappointing for him because he was coming along, playing well and got some growth left. To not be able to have this time to get this experience is always tough.”

Hollins on life on the hot seat. Hollins knows that the Nets’ struggles could cost him his job, but until that time comes, he said he can’t spend time worrying about it. “Every job you have, you’re hired to be fired,” he said. “Whether you win 56 games as I was before, or you don’t win. It’s just the nature of this business . . . All I can do is come to work every day and do my job. And when it’s over, if somebody calls me up and says you’re not here anymore, I pack up and I go home.”

The Nets’ 5-15 record is among the worst in the NBA, and only the 76ers are keeping them from the Eastern Conference basement. Though the front office has publicly supported its coach, Hollins, ever the realist, said he understands the tenuous nature of the position.

“The seat is always hot,” he said. “It was hot when I sat in it the first time . . . I don’t even worry about it. I don’t even think about it. I don’t read about it. When it happens, it’ll probably be a surprise when it does, if it happens. But it’s just a job.”