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 while Popovich is out.

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

Johnson, who was notified two-and-a-half hours before game time that he'd be acting as head coach, told the media that Popovich was "just not feeling well." The Spurs beat the Wolves, 113-103, and Johnson's performance on the sideline earned a rave review from veteran Chris Paul.

"Mitch did a great job, man," Paul said after Saturday's win. "I think our whole coaching staff [did]. Things happen within this league all the time and just like with the players, it's next man. 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.