Serena and Kerber qualify for WTA Finals
Serena Williams and Angelique Kerber have qualified for the season-ending WTA Finals in Singapore.
American Williams and Germany's Kerber, ranked number one and two in the world respectively, are the first two players to seal their places in the prestigious tournament in October.
Williams has not spent much time on court this year, but claimed an Open Era record-equalling 22nd grand slam title by beating Kerber at Wimbledon last month.
"I'm very proud and excited to qualify for the BNP Paribas WTA Finals in Singapore," said Williams
"I have great memories of winning the title in Singapore in 2014 and being supported by so many fans. I can't wait to be back in Singapore later this year to hopefully win my sixth Billie Jean King Trophy."
Kerber has had a year to remember, establishing herself as a major force after winning her maiden major title at the Australian Open back in January.
The 28-year-old would have replaced Williams at the top of the rankings if she had beaten Karolina Pliskova in the Western and Southern Open final last weekend, but was beaten is straight sets.
Kerber said: "I'm so happy to have qualified for the WTA Finals Singapore for the fourth time.
"It is one of the most important events of the year and we all fight to qualify in the top eight. I have great memories from my other experiences at the tournament and I hope to play some great matches and win the title."
Agnieszka Radwanska won the WTA Finals title last year by beating Petra Kvitova.