Stanford sophomore Carol Zhao took her experience at the Bank of the West Classic and flew off to Montreal. Venus Williams will be sticking around for at least another day.
The 25th-ranked Williams downed fourth-seeded and 10th-ranked Victoria Azarenka, 6-4, 7-6 (1) and will meet the eighth-seeded Andrea Petkovic on Friday afternoon.
"It was a great learning experience for me," Zhao said of playing Ivanovic, who will break into the top 10 next week for the first time since 2009. "I can take a lot from this match."
Zhao travels to Montreal -- she's a Canadian citizen -- to compete in the qualifying round of the Rogers Cup this weekend.
"She has a bright future," Ivanovic said. "I think she started a little nervous but when she won a game, she started to relax and play better. All she needs is more experience and confidence."
Zhao won her first WTA Tour match on Tuesday. She led Yanina Wickmeyer, 6-2, 1-0, when the Belgian retired due to a viral infection. It was her second WTA main draw.
Zhao, who is 19, has been entering pro circuit tournaments since 2009, though she remained an amateur to stay eligible for a college scholarship.
Ivanovic, a former world No. 1, represented the highest-ranked player Zhao has meet on the court. She lost to then No. 31 Anastasia Pavlyuchenkova, a Russian, in Toronto last year.
The 2013 Tennis Canada Player of the Year said she'll be working on her serve in preparing for the Rogers Cup.
"It all starts with the serve and I was not able to serve as effectively as I'd hoped," Zhao said. "But she's a top player and that's what top players do: make it hard for you to do what you want."
Ivanovic, in her third appearance at Stanford, advanced to her first quarterfinal. The Serbian, looking for her fourth title of the year, meets top-ranked Serena Williams on Friday.
"It will be a tough challenge but a good test to see where I need to work," Ivanovic said. "It's a different part of the season and a different kind of tournament."
Ivanovic, a former No. 1, recorded three aces and won 75 percent of her first serve points.
In other matches, third-seeded Angelique Kerber beat Coco Vandeweghe, 7-6(4), 0-6, 6-2 and Garbine Muguruza topped Daniela Hantuchova, 6-4, 6-4.
Kerber and Muguruza are playing in their first main draw at Stanford while Hantuchova has made 10 appearances and Vandeweghe, the runner-up in 2012, made her third appearance.
After the 10th-ranked Azarenka, who celebrated her 25th birthday, saved three match points to force to tie it 6-6, Williams won the first five points in the tiebreaker.
"The tiebreaker felt great," Williams said. "It brought out my best tennis. I needed the challenge."
Azarenka's second serve was the biggest difference between the two hard-hitting players. She won just 32 percent of her second serves, handing Williams, who reached her third quarterfinal of the season, a significant advantage.
"We both had good points," Azarenka said. "Venus was a little better on her execution on important points. I have to realistic and look at the things that have to be done. It's not easy being patient but if I wanted easy, I'd go sit on a couch."
Williams, in her 12th career appearance at Stanford, reached her 10th quarterfinal. She has won the twice and finished second five times.
Azarenka won the event in 2010 and has been eliminated in the second round in her last two appearances.
Friday's Order of Play
Garbine Muguzura (Spain) vs. Angelique Kerber (Germany), noon
Sachia Vickery (USA) vs. Varvara Lepchenko (USA), following
Venus Williams (USA) vs. Andrea Petkovic (Germany), not before 4 p.m.
Serena Williams (USA) vs. Ana Ivanovic (Serbia), 8 p.m.
Paul Kania (Poland) and Katerina Siniakova (Czech Republic) vs. Daniela Hantuchova (Slovakia) and Arantxa Parra Santonja (Spain), following
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