Flavia Pennetta, seeded 5th in San Diego, played Samantha Stosur for the third time today, and for the third time, she won in straight sets. Pennetta, serving cleverly and playing a clean match, defeated the 2nd seed 6-4, 6-3. Stosur had only one break opportunity, on which she capitalized. Pennetta, on the other had, had thirteen break opportunities, and converted four of them. The Italian made 14 unforced errors, compared with Stosur's 37.
In the other early quarterfinal, Svetalana Kuznetsova found herself down 2-5 against Coco Vandeweghe in their first set, but she came back to win that set 7-5. She then easily won the second set 6-2. Vandeweghe, who has a formidable forehand, made a lot of backhand errors, and became more careless as the match went on. She concluded the match with 24 winners and 44 unforced errors.
In the third quarterfinal of the day, Daniela Hantuchova defeated Alisa Kleybanova 2-6, 6-4, 6-3. Hantuchova was 0-3 down in the second set, but came back with a better serve for the latter half of that set and the rest of the match. Kleybanova made the final set close, but Hantuchova prevailed.