Two upsets propel Americans into the third round

After three hard-fought sets, American Nicole Gibbs is on to the third round. To get there, she knocked off 23rd seed Anastasia Pavlyuchenkova on another hot, humid day at Arthur Ashe Stadium, 6-4, 6-7, 6-3. Pavlyuchenkova had 15 double faults in the match; Gibbs converted eight of 12 break points. Playing in her third U.S. Open, the 21-year-old Gibbs had never advanced beyond the first round.

It was the second upset of the day for the Americans. Earlier, Sam Querrey pulled off a straight-set upset against 28th seed Guillermo Garcia-Lopez of Spain.

"I felt like I played great today. Serve felt good, forehand felt good, I was making the right decisions. Hope I can keep playing like that," Querrey said after the match.

John Isner, the highest seeded American man at this year's Open, soon joined Querrey in the third round by trumping Germany's Jan-Lennard Struff in straight sets. Isner racked up 30 aces and converted three of six break points.

The second-round success was a welcome end to a tough first week for the American men, as six were eliminated, including Jack Sock, Donald Young and Steve Johnson.

If Novak Djokovic wins today, Querrey will face him in the third round. He anticipates a tough match, but is counting on crowd support. "The crowd here seems to be pretty pro-American, so I'm sure they will be behind me," he said. "If I played like I played today and I'm aggressive and, you know, everything is dropping in, I think I can challenge him and hopefully come out with a win."

Elsewhere on Day 4, top seed Serena Williams easily defeated Vania King, 6-1, 6-0.

American Varvara Lepchenko is also moving on after defeating Mona Barthel in straight sets. That matches Lepchenko's career-best performance – she also advanced to the third round in 2012.

Christina McHale fell to 16th seed Victoria Azarenka, while 11th seed Flavia Pennetta knocked out Shelby Rogers.

Still to come, 15-year-old CiCi Bellis attempts to keep her first-round magic going as she faces Zarina Diyas.

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