WASHINGTON — British top seed Andy Murray suffered a stunning defeat in his first hardcourt warm-up match for the US Open, losing Wednesday to Teymuraz Gabashvili at the ATP and WTA Washington Open. The 53rd-ranked Russian outlasted third-ranked Murray 6-4, 4-6, 7-6 (7/4) over two hours and 42 minutes to reach the third round at the ATP and WTA Washington Open. The 6-foot-10 American John Isner hit 17 aces, won 37 of 40 first-serve points and moved into the third round by beating Victor Estrella Burgos of the Dominican Republic 6-3, 7-6 (5). Murray, the first Washington top seed to lose his first match since Ivan Lendl in 1993, served for the match in the third set and was two points from victory before Gabashvili broke to 5-5 and the Russian later took the final four tie-breaker points to secure the triumph. “It was a tough match,” Murray said. “Obviously disappointing not to close out the third set when I had a chance. Struggled with my rhythm early. There were some good rallies. He served well in the big moments, especially in the third set.” Gabashvili, who was 3-22 against prior top-10 foes, hit 30 winners and only made 15 unforced errors while winning 86 percent of first-serve points in making Murray the highest-ranked victim of his career. Murray, the 2012 US Open and 2013 Wimbledon champion, has much to work on before the Flushing Meadows fortnight begins August 31. Gabashvili, who will next face Lithuania's Ricardas Berankis. Also sent packing was South African fifth seed Kevin Anderson, who lost to German Alexander Zverev 2-6, 6-3, 6-4. Argentina's Leonardo Mayer outlasted Slovenian Blaz Rola 7-6 (7/2), 6-7 (3/7), 6-4, to reach a third-round matchup against Japanese second seed Kei Nishikori. In other matches, seventh-seeded Feliciano Lopez ended Lleyton Hewitt's last appearance at the Citi Open with a 4-6, 7-5, 6-3 victory. Next for Lopez is a match against Sam Groth, who eliminated ninth-seeded Viktor Troicki 6-3, 6-4. On the women's side, Australian second seed Samantha Stosur, the 2011 US Open champion, advanced to a quarterfinal with a 6-1, 7-5 victory over American Irina Falconi. French fifth seed Alize Cornet was upset 7-5, 4-6, 7-6 (7/4) by 19-year-old wildcard Louisa Chirico. Defending champion Svetlana Kuznetsova withdrew due to a lower left leg injury, advancing American Sloane Stephens into the quarter-finals against Chirico. Riske upsets Suarez Navarro American Alison Riske changed her schedule this season to include the Bank of the West Classic for a variety of reasons. One of them was to change her luck. The 59th-ranked Riske did just that, beating third-seeded Carla Suarez Navarro 6-4, 6-4 Wednesday to reach the quarterfinals. It was a tough day for seeded players. No. 69 Ajla Tomljanovic beat the seventh-seeded Madison Keys 1-6, 6-4, 6-1 and Germany's Mona Barthel topped sixth-seeded compatriot Andrea Petkovic 5-7, 6-2, 7-6 (4). Eighth-seeded Elina Svitolina survived the day in the final match, beating Stanford grad Nicole Gibbs, 6-3, 7-6 (5). Thiem in quarters Top-seeded Dominic Thiem extended his winning streak to nine matches by defeating fellow Austrian Andreas Haider-Maurer 1-6, 7-6 (6), 6-4 in the second round of the Generali Open Wednesday. Thiem will now play Albert Montanes of Spain, who beat Diego Schwartzmann of Argentina 6-1, 6-3. Dusan Lajovic of Serbia advanced after his opponent Andreas Seppi pulled out in the second set. The second-seeded Italian trailed 7-5, 3-0 when he quit the match with back problems. Lajovic's next opponent is Nicolas Almagro of Spain, who rallied from 5-1 down in the opening set to beat Jurgen Melzer of Austria 7-6 (4), 7-5. Earlier, Fabio Fognini of Italy and Philipp Kohlschreiber of Germany earned straight-set wins in less than an hour to set up a quarterfinal. Also, French qualifier Paul-Henri Mathieu defeated fourth-seeded Martin Klizan of Slovakia 6-3, 7-5, and will next play Federico Delbonis of Argentina, who rallied to beat two-time former champion Robin Haase of the Netherlands 4-6, 6-2, 6-2. — Agencies