The redshirt sophomore didn't get hit or make any contact with another player, but the step will cost him the rest of his season.
Gardner suffered an injury on that play that will require surgery to his left knee, according to a release by the school on Tuesday.
No date has been set for a surgery.
"It is really unfortunate and disappointing for Will because of how hard he has worked and how respected he is in the locker room," U of L coach Bobby Petrino said. "Will will continue to be an integral part of our program moving forward because of his leadership he has displayed and the respect he has in the locker room."
Gardner started seven games for the Cardinals and threw for 1,669 yards and 12 touchdowns, while throwing just three interceptions.
True freshman Reggie Bonnafon will be the starter for the Cardinals when they face Notre Dame in South Bend, Ind., on Nov. 22 at 3:30 p.m.