Flavia Pennetta has claimed that Roberta Vinci has the ability to cause a shock against Serena Williams in the US Open semi-finals.

The unseeded Vinci is preparing for her first appearance in the last four of a Grand Slam, and Pennetta believes that her fellow Italian will rise to the challenge of facing the world number one, who is bidding for a seventh title at Flushing Meadows.

"I mean, she has to go in the court and try her best. She [doesn't] have nothing to lose. She has in front of her Serena Williams. I mean, you just have to go on court and try everything," Pennetta told reporters.

"She has to believe that she can make it, because if you go on the court you are not that sure or you are thinking, 'Okay, it's done; I'm okay, like this, it's going to be bad'."

Pennetta will take on Simona Halep in the other semi-final after beating Petra Kvitova on Wednesday.