MARTINA HINGIS | Retired at 27: During the 1990s, Hingis set a series of "youngest-ever" records, including youngest-ever Grand Slam champion and youngest-ever world No. 1. In 2003, at age 22, she developed ligament injuries in both ankles, forcing her to withdraw (though temporarily) from professional tennis. She had won 40 singles titles and 36 doubles titles and, according to Forbes, was the highest-paid female athlete in the world for five consecutive years, 1997 to 2001. After several surgeries and long recoveries, Hingis returned to the WTA Tour in 2006, climbing to world No. 6, winning two Tier I tournaments, and also receiving the Laureus World Sports Award for Comeback of the Year. After being hampered by a hip injury for several months, she retired in November 2007.
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