Williams was then transported via ambulance to a local hospital for evaluation. He later returned to Lucas Oil Stadium and was in the trainers' room after the game, coach Chuck Pagano said.
"It was a pretty scary thing ... but he's back here," Pagano said. "He's doing well."
The team said Williams did not suffer an injury to his neck. He got a standing ovation from the crowd and received well-wishes from his teammates before being driven off the field.
Back in 2011 with Chip Kelly's University of Oregon program, Williams was forced to trade in football for basketball when team doctors discovered a spinal stenosis condition that was deemed career-ending. After playing hoops at Portland Bible College in 2012, Williams sought another medical opinion and gained clearance to pursue an NFL career.
NFL players tweeted out their support to Williams following his injury: