Former world number one Andy Murray withdrew from the Brisbane International with a hip problem on Tuesday, further putting in doubt the Briton's prospects of being fit in time for the Australian Open later this month.
US Open champions Marin Cilic and Serena Williams kicked off their China Open campaigns with straight sets victories against battling underdogs on Monday, but Rafael Nadal suffered defeat in a rare doubles outing on his return from injury.
Reigning French Open champion Maria Sharapova, former world number one Venus Williams and Australian Samantha Stosur sailed into the second round of the China Open with straight set victories on Sunday.
