Brooklyn Nets guard Jarrett Jack will miss the remainder of the season with a torn ACL and a small medial meniscus tear in his right knee.

Jack suffered the injury on Saturday afternoon during a contest against the Boston Celtics at the TD Garden. Late in the third quarter, Jack was leading a fast break when he stumbled to the ground and grabbed his leg in pain. A Nets’ trainer and some of his teammates had to escort him back to the locker room without him putting any weight on the leg.

Below is a video of how the incident occurred:

On Instagram, Jack went on to comment on the injury saying “worst pain I’ve ever felt in my life.”

Teammates Joe Johnson and Brook Lopez both spoke about Jack in an interview with the New York Post. “When I saw him on the floor grimacing in pain I knew it was probably something serious and it was tough on him,” said Johnson. Lopez added, “It’ll obviously be tough on us. He’s a huge part of what we do on and off the court, a very vocal presence in the locker room, our leader.”

In 32 games started for the Nets, Jack averaged 12.8 points, a team-high 7.4 assists and 4.3 rebounds. The nine-year pro was drafted by the Denver Nuggets in 2005 and then traded to the Portland Trail Blazers on draft night. He has also played for the Indiana Pacers, Toronto Raptors, New Orleans Hornets, Golden State Warriors and Cleveland Cavaliers. Jack has played a total of 803 games in the league and holds career averages of 11.1 points and 4.5 assists. A surgery date has yet to be set.

With a record of 10-23, Brooklyn will now have to rely on reserves Shane Larkin and Donald Sloan, who were both added to the team in the off-season. Larkin, who has received quality minutes and has been efficient this season, is averaging 6.6 points and 3.8 assists per game. At times this season, head coach Lionel Hollins has ended the game with Larkin on the floor. Sloan holds averages of 2.5 points and 2.2 assists per contest. The Nets will host Boston on Monday night at Barclays Center.