Mike O'Connell participated in men's tennis and men's basketball during his time as a Mighty Oak, graduating in 1972. He scored a career high of 26 points against Union College during his senior basketball season, but saw his highest accolades while a member of the Mighty Oaks tennis team where he was named the OCU Most Valuable Tennis Player, going on to a professional tennis playing and management career. He was named the Indiana USPTA Professional of the Year, while he earned the #1 ranked Player of the Year from 1982-85 and in 1998.

He was the Central Indiana Tennis Association's top-ranked tennis player in singles in 1984, and doubles nine times during a 14 year span from 1984-97. From 1983-93, he won 120 consecutive USTA doubles matches, and in 2009 was named the USPTA Midwest Professional of the Year. He also was inducted into the USPTA Hall of Fame in 1998, his first of two years as Indiana's USPTA President. O'Connell was inducted in the Sullivan County North Central Basketball Hall of Fame in 2018 in recognition of his scoring over 900 points in just two high school basketball seasons. He also was inducted into the Monroe County Hall of Fame in 2019.

Having completed his USPTA Professional Level 1 certification in 1980, he became a United States Tennis Association umpire in 1982, a USPTA Master Professional in 1992, and a National Tennis Rating Program verifier in 1995. From 1976-92, O'Connell served as manager and tennis pro at French Lick Resort. He became the assistant director of programming and head tennis pro at the Indiana University Tennis Center from 1992-2006, when he began serving as the IU Tennis Center Director until 2017.