Center Kristaps Porzingis had surgery to repair his lateral meniscus, the Dallas Mavericks announced Friday.
Porzingis was injured on Aug. 17 during the first game of the Mavericks playoffs series against the Los Angeles Clippers.
The team said Porzingis would begin rehab immediately.
There is no timetable for his return.
During the playoff series, Porzingis continued playing through games 2 and 3, before his knee worsened and he had to sit out the remainder of the series.
Dallas lost to the Clippers in six games.
This isn't the first time Porzingis has suffered a knee injury. He missed all of the 2018-19 season due to an ACL injury.
The Mavericks acquired Porzingis from New York as part of a seven-player trade in July 2019.
He was drafted fourth overall in 2015. Prior to that, he played professionally in Spain.
No schedule has been set for the 2020-2021 NBA season. The Los Angeles Lakers have a chance to win the NBA Finals Friday night against the Miami Heat.