Isner is the last seeded American in the men's draw after No. 26 Sam Querrey lost in four sets to Adrian Mannarino. Another U.S. man, 20-year-old Jack Sock, moved to the third round with a 7-6 (3), 1-6, 7-5, 6-2 win over Maximo Gonzalez of Argentina.
On the women's side, Williams was pushed only briefly against Voskoboeva, ranked 77th from Kazakhstan.
Serving at game point trailing 5-3, Voskoboeva drew Williams to the net, and as Williams reached for the ball, her feet slid out from under her and she fell hard onto her backside, her racket slamming to the ground. Before she fell, however, she reached the shot to win the point. Two points later, she closed out the set.
The second set took all of 27 minutes. When it was over, Williams was sitting at the same table where Errani had cried earlier, being asked how she would advise the Italian, who said she was "destroyed by the pressure" of returning to the French Open this year, where she followed her 2012 appearance in the final with a run to the semifinals.
"I really wouldn't know what to say," Williams said. "I can only say that I think she's doing a good job. I mean, sometimes you have a tough day at the office, and it doesn't mean that you don't handle the pressure well."
But Errani said she didn't.
She is 5-foot-4½ with energy to spare, but with loopy, unthreatening groundstrokes and a serve that maxes out at around 85 mph. It has been, even by her account, heart and grit that helped her get to the 2012 French Open final, then follow that with a trip to the U.S. Open semifinal, where she lost 6-1, 6-2 to Williams.
Those results, plus a tournament win and three second-place finishes on tour this year, made her the highest-seeded Italian woman ever in a major for this trip to Flushing Meadows.
But after a 6-0, 6-0 victory over a 152nd-ranked "lucky loser" in the opening round, Errani previewed what was to come, saying then that her tension was "through the roof" knowing that "everyone expects me to win 6-0, 6-0, or thinks that I can only lose against three other women in this tournament."
Then, after the loss to Pennetta, Errani tearfully acknowledged she couldn't handle the strain.
"For a couple of weeks now, I haven't been well," she said. "There's too much pressure."
It didn't help, of course, that she was playing an opponent with nothing to lose, the way many players react when they face someone in the top-5. Last year, Pennetta missed the U.S. Open and the entire end of the season while she recovered from surgery on her bad right wrist.
Going against a player she's familiar with, Pennetta went for it and hit 33 winners to only 12 for Errani. Pennetta broke serve in the very first game and never looked back.
"I tried to play aggressive from the very beginning and I was perfect today, I think," Pennetta said.
As for her friend's woes — well, Pennetta certainly didn't see them through the same lens as Errani.
"It's nothing tragic for her," Pennetta said. "One match is one match."
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