In 1989, the Blue Jays' new retractable roofed home, SkyDome, opened mid-season. It also marked the beginning of an extremely successful five-year period for the team. In May, management fired manager Jimy Williams and replaced him with Cito Gaston, the team's hitting instructor. The club had a dismal 12–24 record at the time of the firing, but went 77–49 under Gaston to win the AL East title by two games, with an 89–73 record. On May 28, George Bell's walk-off home run, off of Chicago White Sox closer Bobby Thigpen, marked the end of the Exhibition Stadium era. The first game at the new stadium took place on June 5 against the Milwaukee Brewers; the Jays lost 5–3. In the 1989 ALCS, Rickey Henderson led the World Series champion Oakland Athletics to a 4–1 series win.