2015 Madrid Open: Serena Williams enters into the quarter-finals with a three set win

Serena Williams progressed to the quarters win a three-set win over Victoria Azarenka

World No.1 Serena Williams progressed through to the quarter-finals of the Madrid Open on Wednesday, but not after she was stretched by another former top-ranker player Victoria Azarenka in the third round.

The reigning Australian Open champion was down 6-5 and 40-0 in the third set but made a remarkable comeback to smash two winners after which Azarenka, astonishingly served three continuous double faults to concede the game to the 33-year-old Serena.

The American then brought her A-game out in the third set tie-break, clinching it by a whopping 7-1 margin to win the set and the match, 7-6 (7-5), 3-6, 7-6 (7-1).

Speaking after the match, Serena said that the match ebbed and flowed both ways and admitted she didn't quite understand how she managed to pull off a win from such a precarious position.

"I could have won, she could have won. I ended up winning and I don't know how,” she said.

Wozniacki, Kvitova have it easy

Petra Kvitova and Caroline Wozniacki, though had easy sailings through to the quarter-finals, defeating Anastasia Pavlyuchenkova and Agnieszka Radwanska respectively, in straight sets.

Former US Open champions Svetlana Kuznetsova, also didn't have an easy time facing Samantha Stosur of Australia, but eventually won her match as well, 5-7, 6-2, 7-6 (5).