Justine Henin, known between 2002 and 2007 as Justine Henin-Hardenne, is a Belgian retired professional tennis player and former World No. 1. Henin won 43 WTA singles titles and seven Grand Slam singles titles, including four French Open titles, one Australian Open title, and two US Open titles. She has also won the year-ending Sony Ericsson Championships twice and the singles gold medal at the 2004 Summer Olympics. Tennis experts cite her mental toughness, the completeness and variety of her game, her footspeed and footwork, and her one-handed backhand as the principal reasons for her success. Critics and all-time-great players have made testament to Henin's talent. Upon Henin's first retirement from the WTA in the early part of the 2008 season, Billie Jean King said that "pound for pound, Henin is the best tennis player of her generation", as well as that "Justine is the best women's athlete I've ever seen." Andre Agassi said of Henin, "Justine Henin is one of the most talented women ever to have played the game of tennis." In 2007, 18 time Grand Slam winner Martina Navratilova said that "She is head and shoulders above everyone else right now." John McEnroe concurred, saying that Henin is "The player I most like to watch." Henin made a return to the WTA in early 2010, losing the final of the Australian Open in only her second tournament back.