Serena Wiliams came out on Wednesday against the Bulgarian Tsvetana Pironkova.
After conceding the first round 6 games to 4, the former world number 1 was able to rectify the situation by winning the 2nd and 3rd sets 6/3 6/2.
The American will face Victoria Azarenka or the Belgian Elise Mertens in the semi-final.
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