MASON, Ohio (AP) -- John Isner's summer surge ended with an opening-round loss to friend and doubles partner Sam Querrey, leaving the top-ranked American with some things to work out before the U.S. Open.
Querrey proved steady throughout a 6-3, 7-6 (3) victory over the 11th-seeded Isner on Tuesday in the first round of the Western & Southern Open, the first upset on the men's side.
Isner had won 11 of 13 matches on hard courts this summer, winning the title in Atlanta, reaching the finals in Washington and advancing to the quarterfinals in Montreal. He'll rest heading into the Open.
Isner was worn down from the stretch of matches in those three tournaments.
"I have definitely felt better," Isner said. "That's the thing: You put some good weeks together, it can put you in a bit of a deficit the following week. But regardless, it's disappointing to lose."
Querrey improved to 4-1 against Isner. He also beat him in straight sets in the quarterfinals at Memphis this year.
"I know he was a little wobbled there in the first set, but besides that I felt I did everything well," Querrey said. "Didn't make many mistakes. I was happy with how I played."
The Americans have teamed up in doubles for at least two tournaments each year since 2008. They had never played each other in the first round of a Masters event.
"It's not that fun, but you know it happens all the time," Querrey said. "It's just part of the game. After in the locker room we talked like nothing happened, so everything is all fine."
Twelfth-seeded Richard Gasquet beat Australia's Nick Kyrgios 6-2, 6-1; 15th-seeded Kevin Anderson needed three sets to beat Argentina's Leonardo Mayer; and 16th-seeded Grigor Dimitrov beat qualifier Vasek Pospisil in a pair of tiebreakers.
On the women's side, Sloane Stephens got started toward a second championship, beating 10th-seeded Carla Suarez Navarro 6-1, 6-2. She won her first pro title at the Citi Open on Aug. 9 in Washington.
"(You're) always like searching and trying to find that next great moment, and like that was like one Sunday where I had a great moment," said the 22-year-old Stephens, a first-round loser at Toronto last week. "Now, I'm like, 'I need another Sunday. Come on.'"
Stephens served nine aces to Suarez Navarro's two.
"Nine aces today -- boom," she said with a wave of her hand. "I'm working on a lot of things, but that is definitely one thing that I have tried my best to improve on. It's coming around, so that's good."
Russia's Daria Gavrilova beat 16th-seeded Sara Errani of Italy in three sets.
AP freelance writer Mark Schmetzer contributed to this report.
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