The stocky, baby-faced outfielder was first called up to the major leagues in 1998 at the age of 26, in the midst of a famously dominant season by the Yankees. He first played briefly in April, then endeared himself memorably to fans in September by hitting 10 home runs, including 3 grand slams, then a record for Major League Rookies (until it was broken by Alexei Ramirez in 2008), in only 67 at-bats, earning him a spot on the Yankees postseason roster.
Spencer was nicknamed Roy Hobbs, in reference to the protagonist in The Natural, because he hit so many home runs and was older than most rookies when brought up to the majors. He hit a long home run in Yankee Stadium during the Divisional Series against the Texas Rangers, and the Yankees went on to win the World Series.
Spencer was not able to maintain that level of success, but became a solid role player and stayed with the Yankees through the 2002 season, having played in four World Series, winning three. He split the 2003 season with Texas and Cleveland and was signed as a free agent in 2004 by the Mets. His career did not live up to expectations, though, missing much playing time due to injury and striking out too often. In 2005 he signed with the Central League's Hanshin Tigers in Japan, appearing in 108 games and hitting 9 homers. In 2006, he continued to play for the Tigers, but was cut.
Major league teams were reluctant to sign him, despite his major league experience, because of off-field trouble after leaving the Yankees. He cut his foot in a bar in Manhattan, and then, while he was supposed to be on rehab assignment, he was arrested for drunk driving and speeding over 97 mph. He also had problems with Florida police during spring training 2004. He and teammate Karim Garcia were accused of hitting and kicking a pizza delivery man in 2004, though all charges were dropped.