Ketcham was born in Englewood, New Jersey. After attending the Hotchkiss School, he enrolled at Yale University, where he was a member of Skull and Bones. He played every game for Yale's varsity football team in 1911, 1912, and 1913. He helped lead Yale to a 7-2-1 record in 1911 and a 7-1-1 record in 1912 and was a consensus All-American in both of those years. In 1913, Ketcham was selected as the captain of Yale's football team. In a departure from past tradition at Yale, Ketcham appointed Howard Jones as the school's first salaried football coach. Ketcham later recalled: "I played every varsity game for three years and was taken out only once for a slight injury … I am generally credited with having developed the term 'roving center'. Except for today's platoon systems, football hasn't changed materially. We had the on-side kick, the ball was a bit larger in circumference and the drop kick was more popular than the place kick."