During his six years in the NFL, Koy played in 79 games, carried 414 times and gained 1,723 yards. He also has 498 receiving yards with 76 receptions, many from quarterback Fran Tarkenton. In addition, he completed six passes in 12 attempts, with one touchdown and one interception.
Koy was also the Giants' punter with a 38.5 yard average, and returned 30 kicks during his career.
After he retired from the NFL, Koy began a career in banking. He returned to his hometown of Bellville, Texas to work at a savings and loan there. He later worked for Austin County State Bank, which was eventually sold to Wells Fargo.