Hawthorne had a screw inserted after suffering the injury in his fifth metatarsal. He'll miss Illinois' first two games against Missouri and Southern Illinois, and possibly more time.
"He had [the injury] as a junior in high school, and he didn't practice for a week," Illinois head coach Ron Zook said. "He's such a tough kid, he doesn't complain about anything. It bothered him a little bit during camp, but he never said anything, so he kept going.
"You love him because he doesn't ever complain, but if he would have said anything, maybe we would have been able to get away with just giving him a few days off. But he'll be fine and we'll be fine."
The 6-foot, 185-pound Hawthorne started five games as a true freshman last season and recorded 27 tackles, an interception and five pass breakups.
The team announced Thursday that Supo Sanni, the projected starter at strong safety, will miss the season after rupturing his right Achilles tendon in practice.
Adam Rittenberg covers Big Ten football for ESPN.com. He can be reached at email@example.com.