Martina Hingis
Hingis has retired twice from the game. The first time was in 2002, when she was struggling with injuries and was only 22. She returned to tennis in 2005, but retired two years later after sustaining more injuries. A blood test had also proved that she was using cocaine, an illegal drug. In 2013, she returned to playing doubles and became a tennis coach. She won the 2015 Wimbledon doubles title together with Sania Mirza, 19 years after winning her first Wimbledon doubles title in 1996.