Team spokesman Steve Kirschner disclosed Manley's condition roughly four hours before the start of Wednesday night's game. He said the sophomore was to undergo further evaluation and it was not known how long he will be out.
Manley is averaging 4.4 points and 4.3 rebounds in 11.7 minutes per game. He shares the team lead with eight blocked shots and is shooting 55 percent.
The Tar Heels enter their final nonconference game of the season at 9-3, with coach Roy Williams hoping his team shows more improvement.
"We're not as good as I want us to be is the biggest thing," Williams said. "We've talked about we've got to get better as a basketball team. Just trying to get better every day."
Information from The Associated Press was used in this report.