 Warren was drafted by the Detroit Tigers in the twelfth round of the 1979 Major League Baseball Draft out of Fullerton Union High School in Fullerton, California.After going 5-16 with a 5.60 earned run average over two seasons in which he never pitched at higher than the A-ball level, the Tigers released him.He was signed by Oakland shortly afterwards, but was selected by the Milwaukee Brewers rule 5 draft after just one season in their organization.