Gustavo "Guga" Kuerten is a Brazilian former professional tennis player. He was ranked as the world No. 1 in men's singles by the Association of Tennis Professionals for 43 weeks, including as the year-end No. 1 in 2000. Kuerten won 20 ATP Tour-level singles titles, including three majors at the French Open in 1997, 2000, and 2001, as well as the 2000 Tennis Masters Cup. He also won eight doubles titles. ATP world No. 1 from December 4, 2000 to January 28, 2001 — 8 weeks. Wiki link