Spurs coach Gregg Popovich, 75, to be away 'indefinitely' after suffering mystery health issue before game

San Antonio Spurs coach Gregg Popovich fell victim to a health issue before Saturday's game and is now expected to miss a yet-to-be-determined stretch of time, ESPN is reporting.

The 75-year-old is now in his 29th season as an NBA head coach.

ESPN's Shams Charania is reporting that assistant Mitch Johnson will serve as the Spurs interim head coach until Popovich returns.

Johnson filled in on Saturday for the Spurs' 113-103 win over the Minnesota Timberwolves, when Popovich was absent due to an unspecified illness. The win improved San Antonio to 3-3 on the young season. 

Spurs spokespeople did not immediately respond to DailyMail.com's request for comment. 

On Saturday, Johnson dismissed Popovich's issue as a mere illness. 

'He's not feeling well,' Johnson told reporters. '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.' 

The situation now appears to be more serious, although few details are currently available. 

A widower and father of two, Popovich lost his wife Erin in 2018, but has remained in charge in San Antonio, where he’s reached icon status.

Although he’s irritated some locals with his frequent criticism of Donald Trump in deep-red Texas, Popovich is a five-time champion who helped to turn the Spurs into one of the NBA’s most dominant teams of the post-Jordan era.