Deer is famous for hitting the game-tying home run on Easter Sunday in 1987, to give the Milwaukee Brewers their 12th straight win to start the season. The home run was featured on the cover of Sports Illustrated. He also carries the dubious honor of having the lowest official batting average while still qualifying for the batting title when he batted .179 in 1991. He is the only player since 1910 to have a batting average less than .220 in at least 400 at-bats in at least four seasons.
A notorious free swinger, Deer held the American League record for strikeouts in a season (186 strikeouts in 1987) until being passed by Jack Cust in 2008, and had at least 140 strikeouts on seven occasions.