Guillermo Sebastián Coria, nicknamed El Mago, is an Argentine former professional tennis player. He was ranked as high as world No. 3 in men's singles by the Association of Tennis Professionals (ATP), achieved in May 2004. Coria achieved his best results on clay, where he won eight of his nine ATP Tour singles titles, and during his prime years in 2003 and 2004 was considered "the world's best clay-court player." He reached the final of the 2004 French Open, losing to Gastón Gaudio despite serving for the match twice and being up two-sets-to-love. In later years, injuries and a lack of confidence affected his game, and he retired in 2009 at the age of 27. Between 2001 and 2002, he served a seven-month suspension for taking the banned substance nandrolone.