Midway into set two; however, the American picked up her consistency
and served more forcefully take a 5-3 lead before closing out the set 6-3 with a hold of serve behind several aces hit down the tee.
In the final set serving at 1-2, Williams hit two consecutive double faults to fall behind 30-40. Petkovic of Germany then broke serve to reach 3-1 with a crosscourt forehand winner.
Williams broke serve in the following game then held serve to level the set at 3 all. Petkovic then held serve retake the lead at 4-3.
Williams would then commit three forehand errors to drop her service game to trail 3-5 before striking several winners to take the following two games to level the set at 5 all.
Petkovic struck two forehand winners to hold serve to lead 6-5.
<>Serving to stay in the match, Williams hit a crosscourt forehand volley long then hit a crosscourt backhand wide to face match point at 15-40.
A Petkovic crosscourt forehand return winner on a Williams second serve ended the match 6-1, 3-6, 7-5 after 1 hour and 49 minutes of play.
Serena Williams had a similar beginning as her sister in her quarterfinal match as a slow start coupled with aggressive baseline play from Ivanovic of Serbia resulted in the American dropping set one 6-2.
However improved serving and consistency from Williams in set two resulted in the American leading 3-0 and then 5-2; at which point Ivanovic took an injury time out to receive oncourt treatment for her right leg.
Play resumed with Williams maintaining her high level of play to take the second set 6-3 and then lead in the final set 2-0.
Ivanovic broke serve to take a 4-3 lead before Williams took leads of 5-4 and 6-5.
Serving for the match, Williams hit two consecutive aces out wide, her number 9th and 10th aces for the night to lead 40-0.
At 40-15, Ivanovic struck a down the line forehand return wide to end the match 2-6, 6-3, 7-5 after 1 hour and 57 minutes of play.
In today’s semifinals, Williams meets Petkovic while the 3rd seeded Angelique Kerber of Germany takes on Varvara Lepchenko of the USA.