Bagley will have an MRI on Monday, and the Kings have already removed him from the lineup of Sunday's summer-league game against the Los Angeles Clippers. He's also doubtful for Tuesday's matchup with the Memphis Grizzlies.
Bagley was selected No. 2 overall by the Kings in June's draft. The former Duke star is expected to be a major piece of the franchise's ongoing rebuilding efforts.
"I look at Marvin's all-around game," Kings general manager Vlade Divac told reporters after the draft. "He was just hard to pass, the talent Marvin has. ... He can shoot, he can rebound, he can play in the low post. Really, really exciting about the player."
In his lone season at Duke, Bagley earned consensus first-team All-America honors for averaging 21.0 points and 11.1 rebounds per game.
Bagley flashed his potential in Sunday's game, scoring 15 points and grabbing seven rebounds. Losing him for the rest of the summer league wouldn't be a major blow but would deny him the opportunity to continue getting his feet wet in the NBA.