Ana IvanovicUnseeded Ana Ivanovic pulled an upset over No. 21 seed, Zheng Jie, in round 2 of the 2010 U.S. Open.

The former world No 1 from Serbia, who has dropped to 40th in the past year due to injuries and a loss of confidence, produced one of her recent best performances to crush Jie of China 6-3, 6-0 for a place in the last 32.

“I remember a couple years ago when I was here and I was saying, even though I’m No 1 I don’t feel I’m playing as No 1,” Ivanovic said. “But now I feel like I’m playing like a top-10 player, I have confidence that I can beat these players. That’s huge for me.”

Having hit the top of the rankings when she won the French Open in 2008, the Serb’s game and confidence disintegrated and earlier this year she hit a low point of 65th.

But after teaming up with Heinz Gunthardt, who also coached former world No 1 Steffi Graf, her fortunes have begun to turn around.

Against Jie, her forehand was working perfectly and her serve, which had been a serious problem, looked solid.

She hit 22 winners in all and showed no signs of the left foot injury that had caused her to retire from her last tournament in Cincinnati, where she reached the semi-finals.

A leaner-looking Ivanovic said she had put in a lot of physical work in the summer but said her improvement was just as much down to the fact that she has matured as a person.

“Now I feel as if I am just coming up again, and I have really nothing to lose. I got that joy of competing again,” she said.”