"Right now, I think it's doubtful that P.J. will play tomorrow night," Williams said. "Yesterday when I left practice, I thought that he would practice [on Monday], but last night he got a little flu bug and he was throwing up last night and this morning. They've got him over at the hospital right now with some IVs, so I think that postpones some of the things that he could do today in practice that would have gotten him ready.
"I'm not saying that he is not going to play, but I think it's highly unlikely."
Hairston is UNC's top offensive option off the bench and is currently third on the team in scoring (12.4 ppg). The Greensboro, N.C. product is connecting on 46.3 percent of his 3-pointers (19-of-41) in ACC play, including eight of his last 10.
Hairston had scored 48 points in his last 46 minutes of playing time prior to suffering his concussion in Chestnut Hill.
Williams also told reporters that sophomore forward Desmond Hubert was also "sick and throwing up" on Sunday and that James Michael McAdoo didn't practice due to hurting his back late in the game against Virginia Tech.