The Express News reported about the post, which originally showed an image of a receipt that indicated Popovich left a $5,000 tip on a bill for $815.73, at McEwens, a restaurant that serves American food.
According to the report, the handwriting on the receipt matches Popovich's. The bill was from Friday, April 21.
“Coach Popovich has been in our restaurant in the past multiple times,” McEwen's owner Bert Smithe told mySA.com.
Smithe would not say if Popovich dined at the restaurant at the time on the receipt.
“We don't discuss anything that goes on when VIPs are in the building,” he said.
Sports Illustrated reported that the image posted to Reddit has since been deleted, but the Express News took a screen shot of the image.