Markelle Fultz suffered a high ankle sprain in Saturday's Summer League game.
Fultz was helped off the court after rolling his left ankle.
"We will treat him accordingly and be as cautious as we can, making sure he is healthy," 76ers summer league coach Lloyd Pierce said. "We will know [more] once we get some treatment on him. I haven't heard anything [more]."
Fultz was attempting to block a drive in the third quarter when he jumped and landed on the heel of Jabari Brown.
Joel Embiid missed the first two seasons of his career while Ben Simmons missed his first season though he's expected to return for 17-18.
"I'm a little bit punch-drunk with the injuries that we've had with our first players selected over the years,'' said Brett Brown.
Fultz will miss the remainder of Summer League.