Kuminga, the seventh overall pick in this year's NBA draft, was hurt in the fourth quarter of Wednesday's preseason win over the Denver Nuggets.
He joins James Wiseman on the injured list. Wiseman continues to rehab a right meniscus injury suffered last season, and it remains unclear when the No. 2 overall pick in last year's draft will be able to return to the floor.
"It's always disappointing when anybody gets hurt," Warriors coach Steve Kerr said after Thursday's practice. "Especially a young player like Jonathan, like James, missing out on a bunch of training camp, or all of training camp, that's definitely a setback. But he'll be here -- he'll be going through some of the drill work. And he's watching the drill work and understanding what we're trying to achieve. But there's no substitute for actually being out there to start."
Kerr also said veteran swingman Andrew Wiggins did not practice Thursday to rest some "nicks and bruises."
Kerr said there is a chance Wiggins might not play in Friday's preseason game against the Los Angeles Lakers. Stephen Curry and Draymond Green will play a little more than 20 minutes in the game, according to Kerr.
Golden State opens the regular season at the Lakers on Oct. 19.