After his collegiate career, Kelly participated in training camps with the Arizona Cardinals (1992) and Pittsburgh Steelers (1994) of the NFL and spent two seasons playing for the Rhein Fire (1995-96) of the World League.
Kelly is best known for his illustrious career in the Arena Football League, where became the most prolific quarterback in AFL history over the course of his 16 seasons with nine teams. Kelly set several all-time AFL career passing records, including touchdown passes, passing yards, pass attempts and pass completions. In an April 2007 AFL playoff game, he became only the fourth quarterback in football history to throw more than 800 career touchdowns. After retiring from football following the 2007 season, Kelly served as the offensive coordinator for the AFL's Georgia Force in 2008.
Kelly served as a color analyst on regional televised replays of Tennessee's football games with the late Bob Bell a number of years ago before his playing career forced him to give it up. Out of high school, Kelly was the top quarterback prospect in the state of Tennessee after earning Gatorade All-America honors at Rhea County High School in Dayton. Kelly currently lives in his hometown of Dayton with his wife and young daughter.