Former world No.1 Caroline Wozniacki, one point from falling behind 5-0 in the opening set, has rallied superbly to stun ninth-seeded Russian Svetlana Kuznetsova in straight sets at the US Open.
The unseeded Dane, slowed by injuries this season, took advantage of some sloppy play by the former champion to post a 6-4 6-4 victory and advance to the third round.
"It was not looking good for me," Wozniacki said.
"I've been in this situation before. I was down 6-1 (actually 6-2), 4-1 (in the fourth round in 2009) to her once on this court I said 'I can do this, I can pull this through.' And I won last time and I won today and I'm really proud of that."
Wozniacki, twice a US Open runner-up, has struggled through ankle and arm injuries this season and came to Flushing Meadows ranked 74th in the world.
"I stopped looking at the ranking once I fell out of the top 10," said 26-year-old, who has endured a couple of down years. "I feel like I belong at the top.
"Today I beat someone who's been playing really well this year and that's definitely going to build my confidence."
Wozniacki, one of the game's top retrievers, showed no injury effects as she dashed around the court to extend rallies.
Kuznetsova, the 2004 US Open winner, who won at Sydney this season and reached the fourth round at both the French Open and Wimbledon, blamed herself.
"After 4-0 (in the first set) it was very even games, even on my serve," said the Russian.
"Then I made a couple of unforced errors which I shouldn't do and I just let her in the match. And she started to believe.
Two-time Wimbledon champion Petra Kvitova battled into the third round of the US Open with a 7-6 (7-2) 6-3 win over Turkey's Cagla Buyukakcay.
In steamy conditions, the Czech, seeded 14th this year having dropped out of the top 10 for the first time in three years, escaped a first set tiebreak and then broke twice in the second for the victory on the Arthur Ashe Stadium court.
