The Pelicans announced the injury on Monday. He'll be re-evaluated in three weeks.
Williamson sustained the injury on Monday against the Philadelphia 76ers. He pulled up and grabbed his right leg after dribbling up the court. He left the game and did not return. An MRI on Tuesday confirmed the severity of the injury.
The oft-injured Pelicans star had thus far remained relatively healthy this season in leading New Orleans to a 23-14 start that had them a game behind the first-place Denver Nuggets in the West entering Tuesday's NBA slate. News of his injury is a difficult blow for the Pelicans and for Williamson, who has yet to play more than 61 games in a single NBA season.
A torn meniscus limited Williamson to just 24 games during his rookie 2019-20 campaign. He missed the entirety of last season with a foot fracture and a difficult recovery that kept him sidelined longer than expected.
He entered training camp this season healthy and in shape and played in 29 of the Pelicans' first 37 games. He's averaged 26 points, 7 rebounds, 4.6 assists and 1.1 steals while shooting 60.8% from the floor as the Pelicans have emerged as Western Conference contenders.
The Pelicans are also playing without All-Star forward Brandon Ingram, who's been sidelined for 18 games with a toe contusion. Head coach Willie Green told reporters on Tuesday that Ingram is "building up" to a return, but didn't offer a timeline. The Pelicans are 12-6 since Ingram was sidelined.
The Pelicans will rely more on CJ McCollum and Jonas Valanciunas to carry the offensive load while their All-Stars remain sidelined.