Williams' absence increases the chances of world No. 4 Agnieszka Radwanska making a successful defense of her title, which began with the Pole grinding out a 7-, 6-3 win over Yulia Putintseva, a promising 18-year-old wild card entry from Kazakhstan.
The same pole was soon cartwheeling out of the ground again as McCullum, promoted up to number three despite his back concerns, also tried to turn one to leg.