Pironkova won 6-4, 6-7 (5), 6-3 over Alize Cornet
in the fourth round of the US Open on Monday.
In a marathon that spanned 2 hours and 49 minutes, Pironkova's surprisingly successful return to the tour continued as she was the aggressor, firing 46 winners and 50 unforced errors to reach the quarters. The The 30-year-old Bulgarian will once again be an underdog when she takes on No. 3 seed Serena Williams