The Hornets announced that an MRI confirmed the diagnosis of a sprain on Tuesday shortly after the report. They did not offer a prognosis or timeline for his return.
"His return to full basketball activities will be determined by his response to rehab and treatment and further updates on his status will be provided as appropriate," the team statement reads.
A Grade 2 sprain is considered a moderate sprain with a partial ligament tear on a scale of 1 to 3. Per athletic trainer Jeff Stotts of In Street Clothes, NBA players have missed an average of roughly 19 days with Grade 2 sprains.
Ball sustained the injury in the third quarter against the Washington Wizards. He stepped on the foot of Wizards forward Anthony Gill on a drive and rolled his left ankle. He fell to the floor in obvious pain and remained on his back for several moments.
Ball eventually limped to the locker room, and the Hornets ruled him out with an ankle sprain.
After the game, head coach Steve Clifford told reporters that Ball and center Mason Plumlee will miss Wednesday's preseason finale against the Philadelphia 76ers and are listed as day-to-day. Plumlee also sprained his left ankle on Monday. Of Ball, Clifford told reporters: "fingers crossed."
Ball, 21, is coming off his first All-Star appearance in his second season in the NBA. He's one of the league's most promising rising stars. Any extended absence would be an obvious blow to the Hornets, who start their season on the road against the San Antonio Spurs on Oct. 19. They follow up with games against the New Orleans Pelicans, Atlanta Hawks, New York Knicks, Orlando Magic and Golden State Warriors through Oct. 29.
Ball wasn't the only star to injure his ankle in the game. Wizards center Kristaps Porzingis also left the game with an ankle sprain. Head coach Wes Unseld Jr. wasn't too concerned about the injury after the game.
"Just a quick ankle twist, nothing severe," Unseld said.