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Three-time Tour de France champion Alberto Contador tested positive for clenbuterol but he blamed it on food contamination. ((Pedro Armestre/Getty Images))

Rafael Nadal says he hopes that Alberto Contador's doping case will be cleared up soon to stop the "tremendous damage" caused to all sports.

Nadal says on Spanish radio "all of this is horrible for other [athletes]."

The world's top-ranked tennis player cites cycling as the sport most affected by doping, in which "cases arise constantly."

He says "it is tremendous the amount of damage this causes sport and the doubt it casts over other athletes."

Contador, a three-time Tour de France champion, is under investigation for doping and faces a two-year ban.