New York: Italian 26th seed Flavia Pennetta reached her sixth US Open quarter-final on Monday with a 6-4, 6-4 win over Australia's Samantha Stosur, the 2011 champion.
It was the 33-year-old Pennetta's seventh win in seven meetings against the 22nd seed.
"It was my best match of the year," said Pennetta after Stosur, the last woman to beat Serena Williams in New York, committed 35 unforced errors.
"Stosur plays like a Spanish player, with a lot of spin. But I am used to this as I train in Spain.
"I just go to the backhand, try to open the forehand and mix it up a little more."
She will face either Czech fifth seed Petra Kvitova or British qualifier Johanna Konta for a place in the semi-finals.
Pennetta has split her six meetings with Kvitova but has lost the last three, with her most recent win over the double Wimbledon champion coming in the Fed Cup in 2010.
She has never played Konta. AFP
