Missouri’s quarterback competition was abruptly upended Thursday when sophomore Sam Horn left the non-conference game against Central Arkansas after his first snap. Horn kept the ball on a designed run, was tackled by a diving defender, and remained on the turf before being helped to the sideline and escorted to the locker room with what the program described as a lower-body injury. Head coach Eli Drinkwitz had planned to rotate Horn and Penn State transfer Beau Pribula while continuing to evaluate the starting job. Pribula opened the game by directing a touchdown drive, including a long scoring pass, before Horn took the field. With Horn sidelined, Missouri relied on Pribula for the remainder of the first quarter as trainers assessed Horn’s status. Missouri has not provided a timetable for Horn’s return. The Tigers entered the season hoping to settle the position ahead of their Sept. 6 matchup with Kansas State, but Thursday’s development leaves Drinkwitz with an unexpected decision as SEC play approaches.