The 76ers say Simmons will undergo a post-surgery evaluation in approximately two weeks, according to The New York Times' Marc Stein.
Simmons left last Wednesday's contest against the Washington Wizards after injuring his left kneecap while securing a rebound. The floor general exited the league's bubble over the weekend prior to his surgery.
The loss is a significant blow to Philadelphia, as Simmons averaged 16.4 points, a team-high eight assists, and 7.8 rebounds per game. The Australian is also one of the team's top defenders, ranking first league-wide with 2.1 steals per game.
Adding to the 76ers' injury woes, All-Star center Joel Embiid is set to miss Philadelphia's upcoming matchup against the Phoenix Suns on Tuesday with a left ankle injury. However, Embiid isn't expected to be sidelined long term, according to Wojnarowski.