"He's getting better, but he's not practicing," Syracuse coach Jim Boeheim said Wednesday. "He will not play."
Onuaku has not practiced since injuring his right leg during a Big East tournament quarterfinal game March 11 against Georgetown. He's missed NCAA victories over Vermont and Gonzaga.
Boeheim would not say whether Onuaku would be available for a potential Elite Eight game if the Orange defeat No. 5-seeded Butler.
"He will not play [Thursday's] game, that's it," Boeheim said. "That's all I've got."
ESPN.com's Mark Schlabach contributed to this report.