Jarrett Jack, the Nets’ starting point guard and their acknowledged leader, will miss the rest of the season, the team announced Sunday afternoon. Jack severely injured his right knee during the win in Boston on Saturday and will need surgery.

Jack, who was on crutches, said Saturday that when his knee gave out on a fast break, “I never felt pain like that before.”

An MRI exam Sunday indicated that he has a torn anterior cruciate ligament and a small medial meniscus tear. The operation has not been scheduled, but the Nets made it clear that Jack will be out for the season.

After the victory over the Celtics, other Nets players spoke of Jack’s position of leadership on and off the court. His absence will be a big setback for a team that is 10-23 but has shown spunk lately, winning games in Miami and Boston in the past week and generally being in the mix on other occasions, such as a late loss in Orlando this past week. Jack started 32 games and averaged 12.8 points, a team-high 7.4 assists and 4.3 rebounds.

The Nets had enough faith in Jack, 32, to give him the starting point guard job after they let Deron Williams go in the offseason. They acquired Shane Larkin for insurance, and now — barring an acquisition — Larkin will be the starter. He helped spark the Nets to the win over the Heat, as Lionel Hollins chose to start the backup over Jack in the second half.

Larkin also has had some inconsistent moments. In the final 2:02 of the three-point victory Saturday, with the Nets trying desperately to cling to a lead, he committed three turnovers.

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Respect for Jack around the NBA was exemplified in a tweet by Celtics guard Isaiah Thomas after the game Saturday: “Prayers up 4 my guy Jarrett Jack. Minor setback for a Major comeback!”