He was a powerful right-handed pitcher who played for the University of Missouri at St. Louis from 1970 to 1973. In 1972, the UMSL Rivermen advanced to the NCAA Division Two College World Series for the first time in school history. They returned the following year, and Westerholt had the first World Series win in UMSL history, pitching a complete 2-1 victory against Jacksonville State. In 1972, Westerholt had a 4-3 recordwith a 2.66 ERA. He ranked second on the UMSL team in strikeouts. During the 1972NCAA regional playoffs, he pitched in three games on the same day for a total of 14 innings. His ERA was 1.10. In 1973, he had eight wins which was then a single season record and still ranks fourth on the UMSL list. He had five complete games, including two shutouts. His ERA was 2.25. On the UMSL career charts, he ranks third in ERA, seventh in wins, and tenth in strikeouts. Westerholt was inducted into the UMSL Sports Hall of Fame in 2016. His 1972 team was inducted in 2010. Westerholt pitched for Bishop DuBourg High School from 1966 to 1969. From 1970 to 1974, he was a pitcher in the St. Louis County League for the Aalco Tigers.