San Antonio Spurs head coach Gregg Popovich will reportedly be sidelined indefinitely after suffering a health issue over the weekend, according to ESPN’s Shams Charania. Assistant Mitch Johnson is expected to be the interim head coach in Popovich’s absence.

The health issue, which has not been disclosed, surfaced before the Spurs took on the Minnesota Timberwolves on Saturday. The team announced that Popovich, 75, would not be able to coach the game and that Johnson would assume head coaching duties.

Johnson, who was notified that he would be serving as head coach two and a half hours before the game, told the media that Popovich was “just not feeling well.” The Spurs defeated the Wolves 113-103, and Johnson’s performance on the sidelines drew praise from veteran Chris Paul.

“Mitch did a great job, man,” Paul said after Saturday’s win. “I think our entire coaching staff did that. Things happen all the time in this league and just like with the players, it’s the next man up. So shout out to Mitch, he did a great job tonight.”

Popovich is in his 29th season with the Spurs, the longest-tenured head coach in the league. He leads the NBA in wins with 1,391 career victories and another 170 postseason wins. He has also coached five teams to NBA titles.