A former professional baseball player who primarily played as an outfielder. Born on January 19, 1966, he played college baseball at Southern Illinois University Carbondale.

Hillemann was drafted by the San Diego Padres in the 15th round of the 1987 MLB June Amateur Draft. He played in the minor leagues from 1987 to 1992, reaching the Triple-A level. In 1987, he started with short-season Spokane, hitting .285 in 65 games. He then moved up through the Padres' minor league system, playing for teams like Charleston (Class A) in 1988, where he hit .250 and stole 28 bases, and Wichita (Double-A) in 1989, hitting .247 with 27 stolen bases. He made his Triple-A debut in 1990 with Las Vegas.

After his time in the Padres organization, Hillemann was traded to the Milwaukee Brewers and played one more season in 1992 with their Double-A and Triple-A affiliates (El Paso and Denver). Over his minor league career, he compiled a .248 batting average with 21 home runs. He ultimately decided to conclude his baseball career to focus on his family. Following his baseball career, he transitioned to a career in mortgage banking.