The Wuhan WTA tournament in China, had witnessed already four earlier round retirements. All previous four retirements happened after completion of the first set.
The final between Williams and Muguruza, had two players both carrying discomfort. Eventually it was Muguruza, who retired midway the second set with the score 6-3, 3-0 in favour of Williams.
Can we expect a similar number of retirements in Beijing WTA starting
Monday October 5th?
Tennis Betting Retirement Rules 