The junior had started six games last year but found himself in a preseason battle for the job with redshirt freshman Mitch Trubisky. The team's official Twitter account listed Williams as the starter about an hour before kickoff but said Trubisky would play as well.
Williams helped UNC rally from a 1-5 start last year to win a bowl game. He threw for 1,698 yards and 15 touchdowns while running for a team-best 536 yards and six scores.
North Carolina was opening the season with a national ranking for the first time since 2010.