An hour before Game 6 of the Atlanta-Miami first-round Eastern Conference series, the Hawks got a boost and the Heat took a hit.
Williams returned for the Hawks on Friday night, even though Atlanta coach Mike Woodson declared him out just hours earlier citing continued issues with Williams' sprained right wrist.
"He started to shoot this morning," Woodson said Friday night. "I wasn't expecting him back at all."
O'Neal, meanwhile, missed the game because of a slight concussion sustained when the Hawks' Zaza Pachulia struck him in the face during Game 5, with little-used Joel Anthony opening the game in his place.
O'Neal did not practice Thursday or Friday morning, but the Heat believed he would play. Doctors, though, conferred with O'Neal shortly before tip-off and made the decision that he shouldn't go, not wanting to risk other potential problems with the concussion.
"He's still a little bit groggy, still a little bit of a headache today," Heat coach Erik Spoelstra said. "He wants to go."
Williams sprained his right wrist in Game 2, missed the next three games, and the Hawks were bracing to be without their small forward for the remainder of the series.
Williams did some more shooting about 90 minutes before tip-off of Game 6, and was included on the roster Atlanta submitted shortly thereafter.
He checked in with 3:51 remaining in the opening quarter, wearing a wrap on his wrist.
Forward Al Horford was also on Atlanta's active roster and took part in the team's warm-ups, although he, too, was declared out in the morning by Woodson because of a sprained right ankle suffered in Game 5. Solomon Jones started in Horford's place, and Mo Evans started again at small forward.