One of the most exclusive clubs in women's tennis is made up of the players who have beaten both Williams sisters at the same tournaments.
It was at the 2002 season-ending championships that a teenage Kim Clijsters accomplished the Williams double, and in doing so won the title for the first time. Though Clijsters acknowledged that it wasn't a fair fight against Venus - the American lost the first five games of the semi-final and then hobbled off stage with a leg injury - there's no need for an asterisk against the Belgian's straight-sets victory over Serena in the final. It was a result that few, if any at all, had been predicting. Serena had been the dominant force of the tennis year, winning three Grand Slam titles. Plus, Clijsters had never previously beaten Serena. And yet Clijsters surprised everyone at the Staples Center in Los Angeles, and even herself (she hadn't imagined that she could win the match in straight sets).
"It's unbelievable. It's been an incredible week for me. I don't even think I realise what's happening at the moment," Clijsters said. "I worked so hard. You have to always keep fighting."
Just to prove that it hasn't been a fluke, Clijsters returned to Los Angeles the following year and retained the title. What was particularly significant about her victory was that she won a million dollars, which at the time was the larger ever champion's purse at a women's-only sporting event. The only undefeated player after the group stages, she beat Jennifer Capriati in the semi-finals, and then dropped just two games in the final against Amelie Mauresmo (having had a far closer, three-set round-robin encounter earlier in the tournament). It was during the Belgian's 'second career', having returned to tennis after becoming a mother, that she won the WTA Finals for third occasion, beating Caroline Wozniacki in the 2010 final in Qatar.
by Mark Hodgkinson - the author of 'Game, Set and Match: Secret Weapons of the World's Top Tennis Players' (Bloomsbury, May 2015).