Keys has produced a stunning win over seven-time Grand Slam winner Venus Williams.
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Keys had never progressed past the third round in a major prior to the tournament, but claimed a huge scalp over the seven-time Grand Slam winner.
The match began evenly as both players managed to hold onto their respective serves for the opening six games, however Keys broke through in the seventh to open up a 4-3 lead.
The 19-year-old maintained the pressure on Williams and won the two remaining games to gain the upper hand.
Williams came out a complete different player in the second and raced out to a 4-1 lead, before Keys took a 10-minute injury time-out for a thigh injury.
The stoppage broke Williams’ momentum and it wasn’t long before Keys levelled the set at 4-4.
However Williams managed to break her opponents rhythm and win the set 6-4.
Williams looked to be on-track for a semi-finals berth after holding a 3-1 lead in the decider, but Keys held serve and went on to brake back Williams.
The pair then broke each other’s serve once more, before Keys used three match points to book her place in the semi-finals.
Keys will now face the winner of Serena Williams and Dominika Cibulkova.