Stefan left SMU following his third season to pursue his professional career on the ATP Tour, playing from 1987-1995. In addition to reaching the Wimbledon Semifinals in 1990 (partnered with Christo Van Rensburg), he captured three ATP doubles titles: Adelaide in 1989 (Neil Broad), Basel in 1990 (Christo Van Rensburg), and Adelaide again in 1991 (Wayne Ferreira).
Following his retirement in 1995, Stefan taught in Boca Raton, FL before joining the staff of FRC to serve as Director of Tennis, a role he held for over two decades. In the summer months, Stefan serves as the Director of Racquet Sports at Westwood Country Club, where he has managed the program since 2007.