Luol Deng underwent a spinal tap to test for viral meningitis, a person with knowledge of the situation confirmed.
The tests came back negative, and Deng hoped to play in Game 6 against the Brooklyn Nets.
Deng was sent home about 90 minutes before tip-off, Tom Thibodeau said.
"He was in the facility in the morning and got treatment," Thibodeau said. "Came in this evening and got more treatment. I didn't find out until about an hour, hour and a half before the game."