“I sit and wonder, ‘Why such a big difference in treatment and judgment?,'" Halep wrote Friday on Instagram.

The former world No. 1 has won only one match out of five since returning to action in March following news the Court of Arbitration for Sport had cut her suspension from four years to nine months.

World No.8 Emma Navarro, who lost in the second round at the China Open, has also taken a wild card.