Sports fans love to debate and chew the fat over who is the greatest of all time but surely when comes to women's tennis that has come to an end.
Serena Williams will probably never be remembered as the most loved woman to grace the best courts in the world – maybe not even the top ten – but as a player she is out on her own.
The world number one retained her WTA Championships title in Istanbul with a 2-6 6-3 6-0 victory over Li Na at a packed Sinan Erdem Dome on Sunday, even when not at her best.
For much of the week it had seemed inevitable Williams would walk away the winner, but in the end she had to summon up her last dregs of energy to complete a 78th win from 82 matches this season.
Williams has won more matches and more titles than in any other year of her career – her best 12 months since she landed the 'Serena Slam' in 2002, winning the four big events in succession.
At 31 she looks almost unstoppable and a more considered schedule in 2014 should she see her leapfrog Chris Evert and Martina Navratilova who are on 18 Grand Slam singles titles, four behind Steffi Graf.
Williams has proved herself for over a decade and at times this year the 31-year-old looked better than ever.
Along with sister Venus she took the sport to another level and her serve is widely regarded as the best ever.
The likes of Victoria Azarenka, Petra Kvitova and Sabine Lisicki continue to strive to knock Williams off her perch but on recent evidence they will have to wait for some time yet before the GOAT leaves the stage.