Top seed Venus Williams fended off a spirited challenge in her opening match against world No. 87 Magda Linette at the WTA Tour's Stanford Tournament Wednesday as she needed three sets to advance. Former two-time champion Williams defeated Linette 6-3, 6-7 (6/8), 6-2 to reach the quarterfinals of the hardcourt tournament at Stanford University. The 36-year-old Williams is hoping she doesn't suffer a post-Wimbledon letdown and she now has an easy path to the semifinals since her next opponent won't be ranked in the top 200 in the world. Williams will face either Catherine Bellis, who is ranked 203rd, or Sachia Vickery who is one spot back of Bellis in the world rankings. In other matches, fifth seeded Misaki Doi showed no mercy against her Japanese doubles partner Nao Hibino, winning in straight sets 6-3, 6-4 in their second round match. Doi, who is ranked 36th in the world, advances to the next round where she will face either second seed Dominika Cibulkova or Urszula Radwanska of Poland. British No. 1 Konta took care of business, beating Julia Boserup 6-3, 6-1 in just over an hour. Her Stanford debut continues in the quarterfinals where she will face China's Zheng Saisai, who upset seventh seeded Frenchwoman Alize Cornet 6-4, 6-1. Easy for Isner, Monfils US top seed John Isner and French second seed Gael Monfils cruised into the third round of the ATP and WTA Washington Open Wednesday but former world number one Caroline Wozniacki dropped out due to injury while leading. Isner, coming off heartbreaking Wimbledon and Davis Cup defeats, fired 14 aces and dropped only three points on his first serve in a 6-3, 6-4 romp over Australian qualifier James Duckworth. Flamboyant Monfils, who had lost three matches in a row after suffering a mystery illness, fired 10 aces and lost only two points on his first serves in a 6-3, 6-2 victory over Taiwan's Lu Yen-hsun. Wozniacki, a two-time US Open runner-up from Denmark, was leading 7-5, 3-4, when a left arm injury forced her to retire from her second-round match against Aussie top seed Samantha Stosur, the 2011 US Open winner. "It happened at 5-all in the first set," Wozniacki said. "I hit a backhand and I just felt the pain." Next for Monfils is Croatian 16th seed Borna Coric, who downed Japan's Yuichi Sugita 6-4, 6-4. Isner will meet Cypriot 15th seed Marcos Baghdatis, who ousted Australian John Millman 6-2, 6-4, for a quarterfinal berth. Aussie third seed Bernard Tomic fired 12 aces in beating American Donald Young 7-6 (7/4), 6-3 to book a third-round date with Croatian 13th seed Ivo Karlovic, who blasted 19 aces in beating American Brian Baker 6-3, 7-6 (7/4). German 19-year-old seventh seed Alexander Zverev beat US 18-year-old Taylor Fritz 6-4, 6-2. Zverev, ranked 27th, is the youngest to crack the world top 30 since Nadal in 2005. Chardy, Berlocq advance Third-seeded Jeremy Chardy beat past Serbian qualifier Nikola Cacic 6-2, 6-0 Wednesday to advance to the quarterfinals of the Croatia Open. Chardy will next face Carlos Berlocq of Argentina, who was leading 7-5, 3-0 in the second set against eighth-seeded Jiri Vesely of the Czech Republic when his opponent retired because of a shoulder injury. Last year's finalist, Fabio Fognini of Italy, advanced with a 6-4, 6-1 victory over Renzo Olivo of Argentina. Fourth-seeded Fognini is playing in Umag for the ninth consecutive year. Damir Dzumhur of Bosnia-Herzegovina rallied to defeat Thomas Fabbiano of Italy 4-6, 6-1, 6-2. Kohlschreiber beaten Defending champion Philipp Kohlschreiber of Germany and third-seeded Marcel Granollers of Spain both lost in straight sets in the second round of the Generali Open Wednesday. Kohlschreiber was upset by the 104th-ranked Karen Khachanov of Russia 6-4, 6-4, while 2013 champion Granollers was beaten by Adam Pavlasek of the Czech Republic 6-2, 6-4. Khachanov plays Dusan Lajovic in the quarterfinals. The sixth-seeded Serb defeated Mischa Zverev of Germany 6-4, 6-4. Pavlasek next takes on Nikoloz Basilashvili of Georgia, who beat Igor Sijsling of the Netherlands 6-4, 4-6, 6-2. Also, fourth-seeded Paolo Lorenzi of Italy, eighth-seeded Jan-Lennard Struff of Germany and Gerald Melzer of Austria advanced to the quarterfinals.