New Delhi, Aug. 7 -- CANTON, Ohio - Fourth down. Panthers trailing by three. Haynes King took the snap, looked right at his receivers, and did not throw the ball. He tucked it, turned upfield, and ran five yards into the end zone as time expired. The Carolina Panthers' sideline erupted. His teammates had already gone deep. Nobody on the field expected him to keep it.

That was how an undrafted rookie won a preseason game in Canton on Thursday night.

King, a product of Georgia Tech who signed with the Panthers as an undrafted free agent this spring, finished his NFL debut with 21 completions on 34 attempts for 180 yards and two touchdown passes. He added 39 rushing yards and a third score on the ground, the last one a walk-off that gave C...