Thorson injured the knee while running a trick play during the second quarter of last week's bowl game in Nashville. He will have surgery to repair the ligament later this month, and a statement from the football program said there's no current timetable for him to return to practice.
"Thorson will spend the next two-to-three weeks working with the Northwestern athletic training staff on prehabilitation in anticipation of a mid-January surgical repair," the statement from a Northwestern spokesperson said.
Thorson was a redshirt junior in 2017 in his third season as a starter for Northwestern. He threw for 2,844 yards, 15 touchdowns and 12 interceptions in the past year. He is the school's all-time leader in career touchdown passes with 44 and has been a part of two 10-win seasons while leading the team's offense.
Thorson is expected to return to campus for his final year of eligibility next fall, a source told ESPN's Adam Rittenberg.
Thorson gets injured on trick play, Kentucky shows respect
Northwestern's Clayton Thorson goes down with an injury, but Kentucky players approach him on the sideline and wish him the best.