Serena Williams reached the Family Circle Cup semi-finals on Friday by beating number two seed Maria Sharapova 7-5, 4-6, 6-1 while Vera Zvonareva upset top seed Jelena Jankovic 6-2, 3-6, 6-2.
Sharapova, who won only nine of 35 points in a final set during which Williams made only one unforced error, lost to the American for the fifth time in seven career matches.
Williams, seeded fifth, blasted 11 aces and successfully landed 65 percent of her first serves during the two-hour, 30-minute affair to set up a clash with France's unseeded Alize Cornet who upset 10th seed Agnes Szavay of Hungary.
Sharapova and Williams came into the match in form.
The Russian last week clinched her first clay court title, beating Dominika Cibulkova in the final on green clay at Amelia Island, while the American also won her last tournament, two weeks ago at Miami.
Sharapova was happy to take the positives from a tough loss the day before her 21st birthday.
"Considering the success she's had on clay, she was obviously the favourite," she told reporters..
The Russian had a chance to win the first set 6-4 but failed to take it and although she won the second and battled to the end Williams finished much stronger to close out the match.
"If I did take that (first) set point or if I had taken a couple of those important points, I would have won the second and the match would been over in two. So, you know, that's the way it goes and that's the beauty of tennis."
Zvonareva will face fellow-Russian and fourth seeded Elena Dementieva in the other semi-final.
Dementieva eliminated seventh seeded Patty Schnyder of Switzerland 6-4, 6-4.
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