The Mubadala Silicon Valley Classic's string of bad luck continued Thursday when second-seeded Madison Keys, the defending champion, withdrew due to a right wrist injury prior to her scheduled opening match.
On Tuesday, sixth-seeded Serena Williams exited the event with the worst loss of her career, 6-1, 6-0 to Great Britain's Johanna Konta. On Wednesday, top-seeded Garbine Muguruza withdrew prior to her first match because of a right arm injury.
Keys, who won the event when it was played at nearby Stanford University last year, issued a statement Thursday that read in part, "I have been feeling pain in my wrist over the last couple of days and felt worse today.
"This event is one of my favorites and I was looking forward to playing here in San Jose, but want to thank San Jose State University and Mubadala for pulling it together in such a short amount of time. I am excited to come back next year and play in front of your great fans."
Poland's Magdalena Frech, a lucky loser from qualifying, inherited Keys' first-round bye and drew a second-round matchup with Australia's Ajla Tomljanovic. Frech's luck eventually ran out, as she fell 6-4, 3-6, 6-3.
Third-seeded Venus Williams ensured the tournament of having one big name in the quarterfinals, winning her second-round matchup against Great Britain's Heather Watson 6-4, 4-6, 6-0.
Greece's Maria Sakkari cruised into the quarterfinals with a 6-0, 6-1 rout of eighth-seeded Hungarian Timea Babos. Fifth-seeded Romanian Mihaela Buzarnescu eliminated American Amanda Anisimova 7-5, 2-6, 6-1.
Qualifier Allie Kiick advanced to her first career WTA quarterfinal with a 6-4, 5-7, 6-1 win over Great Britain's Katie Boulter in Washington.
Kiick, a 23-year-old Floridian who is ranked 202nd in the world, had one career main-draw WTA win before this week. She is the daughter of former Miami Dolphins running back Jim Kiick.
Her quarterfinal opponent will be China's Saisai Zheng, a 6-4, 6-4 winner over Belgium's Ysaline Bonaventure.
Sixth-seeded Belinda Bencic of Switzerland earned a walkover into the quarters when Japan's Nao Hibino withdrew due to an abdominal injury. Seventh-seeded Croatian Donna Vekic outlasted Hungary's Fanny Stollar in a lengthy third-set tiebreaker, prevailing 6-2, 3-6, 7-6 (13) in a 2-hour, 23-minute battle.
Poland's Magda Linette upset third-seeded Naomi Osaka of Japan 6-2, 3-6, 6-3. Eighth-seeded Yulia Putintseva of Kazakhstan eliminated American Jennifer Brady 7-5, 6-2, and Russian Svetlana Kuznetsova routed Romanian Ana Bogdan 6-2, 6-1.
--Field Level Media