Ruiz was born in Toledo, Castile-La Mancha. He made his professional debut with Atlético Madrid, in 1977. From the 1979–80 season onwards he was an essential defensive unit for the Spanish capital club, rarely missing a La Liga fixture when healthy and helping the side to two major titles; he was part of the team that reached the final of the 1986 UEFA Cup Winners' Cup, appearing in the decisive match against FC Dynamo Kyiv (0–3 loss).