San Antonio Spurs coach Gregg Popovich suffered a health issue before missing a victory over the Timberwolves on Saturday, according to ESPN's Shams Charania.

Spurs assistant Mitch Johnson is expected to be the interim head coach for an indefinite period.

It is unclear what the health issue is for the 75-year-old Popovich.

Johnson said he found out he was taking over coaching duties about two-and-a-half hours prior to tipoff.

"He's not feeling well," Johnson said. "This has happened before. I think everybody's just always got to be ready for the next man up. We've had it with injuries and sometimes people get sick or don't feel well or things come up in life. He's just not feeling well."

San Antonio is on the road against Clippers on Monday, before they face the Rockets in Houston on Wednesday.

The Spurs return home to San Antonio for a matchup with Portland on Thursday.