He will be reevaluated after that timeframe.
Zach Lowe and Adrian Wojnarowski of ESPN first reported the news, noting Fox underwent tests to determine the severity of the setback.
Fox suffered a variety of injuries during his first season in the league, including a partial quad tear, an abdominal strain, a sprained ankle and a back injury. Overall, injuries cost the 2018 No. 5 overall pick nine games as a rookie.
Though he dealt with left Achilles stiffness during summer league in 2018, he ultimately suited up for 81 games during his sophomore season.
Fox showed promising progression last season, averaging a career-high 17.3 points per game while improving his three-point shooting from 30.7 percent as a rookie to 37.1 percent as a sophomore.
That appeared to be a good sign for 2019-20, as first-year Kings coach Luke Walton made it clear right from the start that his squad was going to let it fly from deep.
This season, Fox is averaging 18.2 points, 7.0 assists and 4.0 rebounds in nine games. He is shooting 33.3 percent from beyond the arc.
Sacramento has put together an intriguing roster with the likes of Fox, Harrison Barnes, Buddy Hield, Marvin Bagley III and Harry Giles. If Fox is forced to miss time, the Kings will likely turn to some combination of veteran Cory Joseph and Yogi Ferrell to run the point.