He was a pitcher, third baseman, and shortstop who was drafted by the Montreal Expos in 1973 and the Detroit Tigers in 1974. Viefhaus played in the Tigers farm system from 1974 to 1980. In 1978, he was added to the Tigers Major League roster by manager Jim Leyland. Viefhaus began his baseball career in 1965 with Ellisville in the Khoury League. He played for Ellisville until 1970. He was an infielder and pitcher for Lafayette High School from 1971 to 1973. In 1972, Lafayette won the Missouri State Tournament, and Viefhaus was the winning pitcher in the championship game. The following year, he was named an All-State pitcher at Lafayette. He was also selected to the All-Metro team as a third baseman. In 1972, Viefhaus was a member of the Ballwin team that won the American Legion National Championship. He also played for Ballwin in 1973 and 1974. In 1974, Viefhaus was a shortstop on the Meramec Community College team that won the Junior College National Championship in Grand Junction, Colorado. He was the Most Valuable Player of the JUCO tournament. He also received the Best Defensive Player Award. He set a record for most home runs in a JUCO tournament. In 2007, he was selected to the JUCO Golden Anniversary team. In 1974, Viefhaus was honored as the St. Louis Amateur Baseball Player of the Year. He was the top amateur draft choice in the St. Louis area. From 2001 to 2006, Viefhaus managed youth baseball teams in Ellisville and Ballwin.