EVANSTON, Ill. (AP) — Northwestern quarterback Clayton Thorson has a torn anterior cruciate ligament in his right knee, throwing his future up in the air.

He will work with the athletic training staff to prepare for surgery in mid-January, the school said Tuesday. There was no timetable for his return.

Northwestern’s winningest quarterback, Thorson announced last month he would return for his senior season. He was then injured catching a pass on a trick play during a win over Kentucky in the Music City Bowl on Friday. Thorson came up clutching his right knee after being tackled and left the field on a cart.

The preliminary exam indicated no serious injury, coach Pat Fitzgerald said after the game. Subsequent tests revealed the tear.

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