He played in 246 La Liga games over the course of 13 seasons, representing in the competition Real Madrid, Rayo Vallecano, Málaga and Betis.
A product of Real Madrid's youth system, Madrid-born Contreras picked up a UEFA Champions League winner's medal in 1998, even though he did not play a minute during the season.
He spent four years with the B-side, Real Madrid Castilla, and appeared in four first-team games in the 1998–99 campaign as the former finished runner-up; for 1996–97, he was loaned out to Rayo Vallecano where he only missed one league match in 42, being however relegated from La Liga.
Contreras signed for Real Betis in the summer of 2003, making 22 league appearances during his debut campaign but none in the following due to injury and the rise of Toni Doblas.
[8] Contreras was third-choice for the Spain national team in the 2002 FIFA World Cup, a late addition to coach José Antonio Camacho's squad after first-choice Santiago Cañizares was injured in a freak accident.