Gallego, a member of the A's 1989 World Series championship team who played eight seasons in Oakland, will join Ty Van Burkleo (hitting), Ron Romanick (bullpen), Don Wakamatsu (bench), Tye Waller (first base) and Curt Young (pitching) on Geren's staff.
Gallego, 47, has spent the last four seasons as third base and infield coach for the Colorado Rockies. The Whittier native played a prominent role in the 2007 Rockies winning the National League pennant and making the franchise's first appearance in the World Series. That Colorado club established a major league record for highest fielding percentage in a season (.98925) and was particularly buoyed by two infielders, as shortstop Troy Tulowitzki led the majors in fielding percentage at his position (.987) and Todd Helton topped all National League first basemen (.999).
Serving nine years in the Colorado organization, Gallego previously spent the 2000-04 seasons primarily as the Rockies' roving infield coordinator. He did briefly join Clint Hurdle's big league staff on May 1, 2002, but after completing that season, he returned to his minor league position in 2003. Prior to his Colorado stint, Gallego worked as Boston's minor league infield instructor in 1999.
As a player, he played 1,111 games over 13 seasons in the major leagues with Oakland
He was originally selected by the Athletics in the second round of the 1981 June draft out of UCLA.