Krunic shocks Kvitova
Wimbledon champion Petra Kvitova became the latest big-name casualty in the women's draw at the US Open with a shock third-round loss to qualifier Aleksandra Krunic.
Kvitova has never been beyond the fourth round at Flushing Meadows but the Serbian was still a most unlikely giant-killer.
Kvitova's first two performances had raised hopes that she could break her hoodoo this time, but she could not break down the stubborn Krunic and lost 6-4 6-4.
The 21-year-old Serbian, ranked 145th, had never won a grand slam match before this tournament, but followed up her upset of Madison Keys with an even bigger scalp.
Kvitova, who had her right thigh heavily strapped, looked to have turned things around when battled back from 4-2 down to 4-4 in the second set, but Krunic did an exceptional job at making the Czech hit one more ball.
Krunic also came up with some terrific shots of her own, showing remarkable composure for a player who had never taken a set off a top-30 player prior to this tournament.
When Kvitova sent her final forehand wide, the Serbian fell to the ground in celebration.
"It was an honour to play on the same court as Petra, she's a great champion. I watched both her wins at Wimbledon," said Krunic.
"I wanted to be myself on court, play as long as possible. I didn't expect to win. I hoped to win a set."
Krunic said she tried not to think about nerves even as a 4-2 lead in the second set was swallowed up by Kvitova who pulled level at 4-4.
But the slender Serbian broke for 5-4 and claimed her famous win on a second match point when another Kvitova forehand sailed wide.
"On match point I thought 'Don't serve a double fault.' I just wanted to keep the ball in until she missed," added Krunic.
There are now only five of the top 10 women's seeds left in the tournament, with Kvitova joining Simona Halep, Agnieszka Radwanska, Angelique Kerber and Ana Ivanovic in falling early.
Serena Williams made it a hat-trick of victories over fellow Americans to move into the second week without having yet dropped a set in New York.
The top seed and world No 1 had a much tougher time of it against Varvara Lepchenko than she had against either Taylor Townsend or Vania King but was ultimately a convincing 6-3 6-3 winner in breezy conditions.
Williams, who had lost a total of five games in her first two matches in a quest to win a third successive US Open title, battled for 95 wind-blown minutes against the left-hander.
Lepchenko, who is of Uzbek descent, had not won more than two games in a set against Williams in their two previous meetings.
She was also looking to become only the second left-handed player after Ekaterina Makarova to beat Williams at a grand slam, but the two-time defending champion clinched victory after an hour and 35 minutes, despite a spirited effort from Lepchenko.
"My opponent today was spectacular. It was really a good match and it just shows how far Varvara has come, so I'm really proud of her," Williams said.
The American next plays Estonian Kaia Kanepi, who upset 15th seed Carla Suarez Navarro 7-5 6-0.