Stanford sophomore Carol Zhao was in control of her match with Yanina Wickmeyer on Tuesday in the first round of the Bank of the West Classic, leading 6-2, 1-0, with five aces.
That's when Wickmeyer, ranked No. 65 in the world and winner of three WTA singles titles, retired due to a viral illness.
"Too bad we couldn't finish the match but a W is a W," Zhao tweeted. "Very happy with how I played today."
Zhao, who reached the main draw with two three-set victories in the qualifying tournament, advances into the second round where she will meet Serbia's Ana Ivanovic, a 7-6 (2), 6-1 winner over Germany's Sabine Lisicki.
"It's definitely an amazing experience," Zhao said. "Getting my first WTA win was special."
Zhao, playing as an amateur, has had a productive summer already, having played three matches in the qualifying tournament of the Kentucky Bank Tennis Championships before playing her third match at Stanford.
"I didn't know what to expect going in," Zhao said. "This is my fourth tournament and it's a great opportunity."
Zhao, who earned All-America honors after advancing to the round of 16 at the NCAA Singles Championship, enjoyed an impressive freshman season and was named the ITA Northwest Region Player to Watch.
This summer she's been helped by Stanford grads Kristie Ahn and Nicole Gibbs, who freely offer their advice.
An All-Pac-12 second team pick, Zhao earned a final No. 22 national singles ranking after finishing 30-7 overall, 19-2 in duals, playing mainly at the No. 3 spot. She won 17 consecutive matches between Jan. 19-April 12.
Zhao and Ahn lost a tough doubles match to Caroline Garcia and Shuai Zhang, 3-6, 6-1, 12-10.
"Doubles was hard to swallow," Zhao said. "You hate losing when you're so close."
Venus Williams, making her 13th appearance in the Bank of the West, downed qualifier Paula Kania of Poland, 6-3, 6-2, and will meet fourth-seeded Victoria Azarenka in the next round on Thursday at 7 p.m.
Williams, currently ranked 25th, has won all three previous meetings with the 10th-ranked Azarenka.
After going 16 months between tournament titles (Oct. 2012 - Feb. 2014), Williams continues to believe in her ability to compete for another Grand Slam title.
"That's why I work through all the issues," she said. "It's all a build up so I can play competitively. While I'm here I'm going to go for it."
In other singles matches, Monica Puig topped Carla Suarez Navarro, 6-3, 7-5, Garbine Muguruza knocked off defending champion Dominika Cibulkova, 6-2, 4-6, 6-2 and Daniela Hantuchova bested Paula Ormaechea, 6-3, 6-4.
In other doubles matches, Varvara Lepchenko and Ajla Tomljanovic beat Mari Osaka, 6-1, 6-0 and Alla Kudryavtseva and Anatasia Rodionova downed Mirjana Lucic-Baroni and Karolina Pliskova, 6-1, 6-0.
Wednesday's Order of Play
Monica Puig vs. Sachia Vickery, 11 a.m.
Varvara Lepchenko vs. Agnieszka Radwanska, not before 1 p.m.
Mari Osaka vs. Andrea Petkovic, following
Serena Williams vs. Karolina Pliskova, 7 p.m.
Chan-Petkovic vs. Kania-Siniakova, following
Hantuchova-Parra vs. Gavrilova-Xu, 1:30 p.m.
Garcia-Zhang vs. Muguruza-Suarez Navarro, not before 3 p.m.