Caroline Wozniacki was last night knocked out of the US Open in the third round by the world number 136, the Italian qualifier Camila Giorgi.

The Danish sixth seed lost 4-6, 6-4, 6-3 to a 21-year-old who had not played since Wimbledon, where she withdrew with injury after making the third round.

Wozniacki had looked energised after winning a tough first set, but then proceeded to hit just two winners in the next, compared to her aggressive opponent’s 17.

Her success, Giorgi told media after the game, wasn’t rocket science. ”Just when the ball came, just hit the ball in the corners,” she said.

In total, she hit 46 winners and 45 unforced errors, compared to Wozniacki’s 13 and 27.

After the game, Wozniacki blamed her lack of aggression and reliance on pure defence in the second and third sets on the combativeness of the Italian.

“It’s tough to be really aggressive when someone is just going for every shot,” she said.

“I felt like I needed to push her back, but she took very high?risk shots, and things were going in for her. She was going for the lines and she was hitting them when she wanted to.”

It is the fourth time Wozniacki has lost to a player outside the top 100 this year, and the loss continues a dreadful run at the grand slams that has seen her fail to advance past the last 16 at her last seven.

Since making the last four at the 2011 US Open, her grand slam record reads: quarter-finals, third round, first, first, fourth, second, second, third.

“It wasn’t the best year for me at the majors," she conceded at the press conference. "But there is next year."