Flat graduated from the University of Tennessee and turned pro tennis in the early 1990s, but was never as successful as his older brother Ken .
While Flach was not able to celebrate any great successes in singles, he achieved two tournament wins on the ATP World Tour in doubles . In 1991 he stood at the side of Diego Nargiso in Long Island for the first time in a final. He celebrated his first victory in 1993 with Paul Annacone in Beijing . He won his second and last double title at the side of Sandon Stolle in Newport . In the course of his career he was also in a final four times. He reached his highest ranking in the tennis world rankings in 1994 with position 108 in singles and in 1983 with position 73 in doubles.
His best individual result in a Grand Slam tournament was reaching the third round at Wimbledon in 1996, where he defeated Andre Agassi in the first round . In the doubles competition he reached the second round of the French Open , Wimbledon and the US Open .