Most of his professional career was associated to Real Madrid, for whom he appeared in 372 competitive games in nine years, winning a total of ten titles.[2]
A product of La Liga powerhouse Real Madrid's youth system, Madrid-born Gallego made a quick impression with the first team, appearing in 26 matches in his first year and being a midfield mainstay the following seasons as he totalled 250 top-division matches with the conquest of, among others, four leagues, two Copa del Rey and consecutive UEFA Cups (1985–86); blessed with physical and technical ability alike, he could operate with equal efficiency as sweeper.[3]
Following a brief spell with Italy's Udinese Calcio, Gallego returned to Spain and the Spanish capital, spending one season with Rayo Vallecano in the Segunda División and achieving promotion. Retiring at 33, he then worked with his first and last clubs in directorial capacities.[7][8]
After being used only once in that tournament, Gallego became a nuclear defensive player in the next two competitions: UEFA Euro 1984 (a runner-up finish) and the 1986 FIFA World Cup, retiring from international play after Euro 88.[9] In mid-August 2011, he reunited with his former Spain and Real Madrid teammate José Antonio Camacho, acting as his assistant in the China national team.[12]