The Tar Heels did not disclose the extent of the injury or how Williams sustained it, only revealing that he would not participate in the team's 15 spring practice sessions. Williams "will return full speed in August."
UNC's spring practices began on Saturday and will end on April 11. Backup Mitch Trubisky, with whom Williams split quarterback duties for the first part of last season, will take over the first team during the spring. Williams is expected to return for fall practice.
According to UNC quarterbacks coach Keith Heckendorf, the team still expects Williams to take part in practice, if not in his usual capacity.
"I want [Williams] to get as much out of spring ball as anyone." Heckendorf said. "When he walks off the practice field I want him to be exhausted mentally from concentrating on every read and every play on every progression on every defense."
Heckendorf added that Williams remains the starter, but said that the competition for the position had not closed.
As a junior last season, Williams led the team with 3,068 passing yards on a 63.1 completion percentage and 788 rushing yards on 193 carries. He threw for 21 touchdowns with nine interceptions and added 13 rushing touchdowns.
Williams was third among quarterbacks in the ACC in passing efficiency. His rushing total ranked No. 12 among quarterbacks in the country, while his rushing touchdowns total was tied for No. 4 among quarterbacks.
The Tar Heels finished the 2014 season 6-7 overall and 4-4 in the ACC. The team will open the 2015 season Sept. 3 against South Carolina.