Williams, who ended his holdout Tuesday, did not pass his physical because there was discomfort when he put on his helmet. Williams underwent surgery to remove a growth on his head in the offseason.
Redskins interim coach Bill Callahan said that Williams would have passed the physical otherwise. He said he wasn't sure if Williams needed to have a specially-designed helmet.
The Redskins were given a two-week roster exemption for Williams. There's no guarantee he plays for Washington again.
"I'm hopeful that he does," Callahan said. "I have a lot of respect for Trent. He's one of the more elite offensive linemen I ever had the privilege to coach. He has all the ingredients; he has that makeup."
Williams was unavailable for comment, but Callahan said he spoke with him for an hour at the facility Wednesday. Callahan has coached Williams since 2015. Williams, according to multiple sources, was holding out in part because of dissatisfaction with Washington's medical staff. However, it's not clear what part of the staff has caused him the issues. Williams has not spoken publicly since his holdout began.
"His heart's in the right spot," Callahan said. "Trent loves football. Nobody loves football more, that's into it, that studies the game, that really gets into the matchups. There's no question he has a love and passion for playing football."
Williams had told multiple people in the organization that he would not play for the Redskins again. Washington did listen to trade offers before Tuesday's 4 p.m. deadline, but had set a high asking price that no team came close to meeting.
Williams reported before that deadline, otherwise he would have needed the team to apply for his reinstatement with the commissioner's office. By returning -- once he's on the active roster -- Williams would get credit for one season and therefore exit 2019 with only one year left on his contract. There's a good chance the Redskins try to trade him in the offseason.
Williams was in the locker room around 7 a.m. and did attend team meetings. He was not on the field during Washington's practice.
Teammates know this situation isn't settled.
"He has decisions to make and obviously it's not ironed out yet, but obviously you want to see him here," Redskins tackle Morgan Moses said. "Selfishly I want to see him playing with me, with the guys. He's his own business. He has some things he needs to take care of and until he feels that those needs are answered you got to wait and see if he plays or not.
"I'm just happy to see him around here and back with the team. Whatever he has to do upstairs, that's what he has to deal with, and knowing him he'll get it right."
Donald Penn has started at left tackle in place of Williams for the Redskins (1-7) and will continue to do so until he returns. Moses, though, hopes that Williams eventually gets back into the starting lineup.
"You hope," Moses said. "He's here and that's the first step."