The Boston Celtics could be without star forward Jayson Tatum until the 2026-27 season.

The six-time All-Star underwent surgery to repair a torn right Achilles tendon, the Celtics announced on Tuesday.

No public timetable for a return has been revealed, but Achilles recovery is typically a year-long process.

Tatum, 27, sustained the injury in the fourth quarter of the Celtics’ Game 4 loss to the New York Knicks on Monday.

Tatum lunged for a loose ball before immediately crumpling to the floor in pain. He remained on the floor until trainers could help him up, and he was carried into the tunnel without putting any weight on his right foot.

An MRI on Tuesday confirmed the Celtics’ fears he had sustained a severe injury.

Jayson Tatum today underwent successful surgery to repair a ruptured right Achilles tendon. No timetable is currently available for his return, but he is expected to make a full recovery. Further updates will be provided when appropriate. pic.twitter.com/TTXziFtMQB

— Boston Celtics (@celtics) May 13, 2025

In the short term, Tatum’s absence puts Boston in an even deeper hole as they face a 3-1 deficit in their second-round playoff series.

The Celtics host the Knicks in Game 5 on Wednesday.

The long-term effects could be even more devastating for the reigning NBA champions.

Due to a hefty luxury-tax bill looming, some of Tatum’s team-mates may end up on new teams next season.

Al Horford and Luke Kornet will be unrestricted free agents after this season, and Kristaps Porzingis’ contract expires after next campaign.

Tatum and Jaylen Brown are both under contract through the 2028-29 season.

Tatum was voted to the All-NBA First Team in each of the previous three seasons and is a likely candidate to be on the 2024-25 First Team.

The third overall pick in 2017, Tatum has been among the NBA’s most durable stars, playing 585 career games for the Celtics.

He has averaged 23.6 points, 7.3 rebounds and 3.8 assists over eight seasons.

Tatum averaged 26.8 points, 8.7 rebounds and 6.0 assists this season while shooting 45.2 percent from the field.