Dietz has been involved with amateur baseball in the St. Louis area for over 45 years as a player, coach, and manager. A right-handed pitcher and first baseman, he played for Francis Howell High School from 1974 to 1977. In 1976 and 1977, he was named All-Conference and All-District. He was team captain in 1977 when Francis Howell won both the conference and district championships. He was a standout pitcher for Francis Howell. In 1977, he tied the school record for most wins in a season. Dietz received a baseball scholarship to East Central Junior College, where he played from 1977 to 1979. Later, he received a baseball scholarship to Lindenwood College, where he pitched from 1979 to 1981. It was one of the first baseball scholarships ever offered by Lindenwood. In 1980, as team captain, he pitched his Lindenwood team to the conference championship. He received All-League honors while setting school records for most games pitched, most wins, and most strikeouts. In 1978, he played in the Four Rivers Independent League for Sullivan, Missouri. He was selected to pitch in the Four Rivers all-star game. In 1979, Dietz pitched for the St. Charles Travelers in the Metro-Collegiate League. From 1976 to 1991, he played for Cottleville & Harvester in the Eastern Missouri Baseball Association. During those 16 years, he won 62 games while only losing eleven games. His composite batting average was .322. His C&H teams made twelve playoff appearances, winning nine East League championships and seven EMBA championships. He played in five EMBA all-star games and was chosen as the MVP of the 1980 all-star game. In 1980, the C&H Athletic Association presented him with the Fred Banze Award. In 1977, Dietz played American Legion baseball for St. Peters Post 313. The manager of the team was former Major League pitcher Ken Heintzelman. In 1982 and 1983, Dietz was the pitching coach for the C&H Post 462 American Legion baseball team. From 2008 to 2014, he was the pitching coach of the Elsberry Post 226 American Legion team. This team made the state playoffs in 2012 and 2013. Dietz has coached little league baseball for many years, and he has provided pitching lessons to young players. In 2017, he was inducted into the St. Charles County Amateur Sports Hall of Fame.