Agnieszka Radwanska has added 18 time Grand Slam champion Martina Navratilova to her coach staff.
Maria Sharapova recovered from a second-set meltdown to record her first victory at this year's WTA Finals with a 7-5, 6-7(4), 6-2 triumph over Poland's Agnieszka Radwanksa on Friday but the Russian still bowed out of the elite eight-woman tournament.
Top seed Andy Murray could meet Roger Federer or Kei Nishikori in the third round, while Serena faces tricky Belinda Bencic in opening round
It proved a happy Halloween for Czech Petra Kvitova after she made the most of coming back from the dead to set up a title-match showdown with Agnieszka Radwanksa at the WTA Finals.
Top seed Serena Williams shook off a spirited attempt by Agnieszka Radwanska and moved into the final of the Rogers Cup with a 7-6(3), 6-4 victory on Saturday and will meet Romania's Sorana Cirstea, whose surprising run continued when she beat China's Li Na 6-1, 7-6(5).
Swiss qualifier Timea Bacsinszky continued to swipe past the seeds at the Wuhan Open on Wednesday by dumping World No 4 Maria Sharapova from the hard court tournament with a 7-6(3), 7-5 victory.
Second seed Garbine Muguruza, bidding to add the Wimbledon crown to her French Open title, was sensationally beaten in the second round on Thursday by Slovakian qualifier Jana Cepelova 6-3, 6-2 in the shock of the tournament so far.