Cox, who was from Monongahela, Pennsylvania, was drafted by the Cleveland Browns as a running back. But after a back injury he became a kicker, joining the Vikings in 1963, ESPN reported.
He went on to play for the Vikings until 1977, scoring 1,365 points and making him the team's all-time leading scorer to this day, the Pioneer Press reported. He had 282 field goals as one of the last straight-on place-kickers, ESPN reported.
Cox had the idea for a soft football that would allow kids to kick it without getting leg injuries. That was in 1972. He worked with John Mattox and made a mold of a football and filled it with foam rubber, creating the NERF football. His agreement with Parker Brothers for the football, which transferred to Hasbro continued to bring income in for Cox, the newspaper reported.
NERF stands for Non-Expanding Recreational Foam, CBS Sports reported.
"The weight was right. When you threw it, it flew like a football," Cox said, according to ESPN.
He was a chiropractor for 16 years after he retired from the NFL, the Pioneer Press reported.
Cox had heart and kidney issues in recent years and was in hospice care at his home in Monticello, Minnesota, the Pioneer Press reported.