Serena Williams has one more round-robin match to play to reach the semi-final of the WTA Championship, coming from her opening match demolition of Angelique Kerber in the Red Group.
The world number one recorded her second win at the Sinan Erdem Dome in Istanbul on Wednesday against Agnieszka Radwanska, in a contest that ended 6-2, 6-4 in favour of the American.
It was her eighth successive victory over the Polish beauty, who was only able to convert one of the eight break points she created. Williams’ next game will be against Petra Kvitova.
“She definitely played pretty well but I can always look to improve on some things,” Williams said in the post-match interview via BBC News.
“My serve wasn’t as good, but you can’t expect it to be great every day.”
The WTA championships brings together the top eight players in the world with the two best players from each group of four qualifying for the last four.
In the white group, Serbia’s Jelena Jankovic beat second seed Victoria Azarenka 6-4, 6-3 in her opening match.
Jankovic capitalised on 40 unforced errors to beat Belarusian Azarenka.
Azarenka, who won her first match against Italy’s Sara Errani, can still reach the semi-final as she look to return to winning ways on Friday.
China’s Li Na, also playing at the WTA Tour Championship for the first time, overcame Errani 6-3, 7-6 (7-5).