Memphis Grizzlies superstar Ja Morant will miss Sunday night’s game between the Western Conference’s top two teams due to an AC joint sprain in his right shoulder, the team announced.

The Grizzlies did not announce a timetable for Morant’s recovery beyond the road game against the West-leading Oklahoma City Thunder.

Morant underwent season-ending surgery in January to repair a torn labrum in his right shoulder. He was cleared for basketball activities in July and has averaged 21.2 points and 7.9 assists for the 22-10 Grizzlies this season.

Morant, a two-time All-Star, suffered a sprained ACL when he hit a hard screen set up by New Orleans center Daniel Theis during the Grizzlies’ 132-124 victory over the Pelicans on Friday night. The collision caused Morant to fall to the ground and was initially ruled an offensive foul, but the decision was overturned via replay after the Pelicans challenged.

Sunday’s game marks the 13th game Morant has missed this season due to various injuries, putting him at risk of missing the league’s minimum 65 games required to qualify for All-NBA honors and others qualify for important awards. The Grizzlies went 8-4 without Morant this season.

The Grizzlies also provided updates on injuries to two key reserves, guard Marcus Smart and forward Santi Aldama.

Smart was diagnosed with a partial tear of the proximal extensor hood of his right index finger, an injury he sustained in a Dec. 21 win over the Atlanta Hawks. He will be reevaluated in two weeks.

Aldama is being considered week-to-week after suffering a left ankle sprain in the team’s win on Thursday against the Toronto Raptors.