After such a promising beginning, things went swiftly downhill for Sheffield in Milwaukee. First, he became angry because he was shifted back to third base to make room for rookie Bill Spiers. Then Sheffield hurt his foot, but the team doctors found nothing wrong with it. He was accused of faking the injury and shipped back to Denver. Sheffield consulted his own doctor, who found a broken bone. After that, there was no trust between Brewers management and Sheffield. He often criticized his teammates, made errors at third base, and was frequently booed by fans. Sheffield crowded the plate and pitchers threw at him, and he complained that Brewers pitchers didn't retaliate. He later admitted that he sometimes purposely overthrew first base to show his disdain for the team.
During the 1990 season, Sheffield took an unauthorized leave from the team and ended up hospitalized with an unexplained illness. In spring training the next year, he was fined for refusing to run sprints. Sheffield hit .194 in 1991, playing in only 50 games because of injuries and turmoil. Finally, before the 1992 season, he was traded to the San Diego Padres, and Sheffield was overjoyed. "Everything you asked for in Milwaukee, you didn't get," he told Tim Kurkjian of Sports Illustrated. "Ask for good weather, you don't get it. Ask for a good playing surface, you don't get it. Ask for a first-class organization, you don't get it."