Serena won her 18th straight match in New York and reached her first Grand Slam quarterfinal of 2014 with a 6-3, 6-3 win over Estonian slugger Kaia Kanepi in 64 minutes at Ashe Stadium.
The five time champion is on course to become only the second woman to win three consecutive US Open titles since the Open Era began in 1968 and is now 4-0 lifetime against Kanepi since their first meeting in 2009.
“She hits the ball incredibly hard and moves the ball around,” the world No 1 said afterwards to the crowd watching on in Arthur Ashe Stadium. “I just keep fighting.”
“I finally made a quarter-final this year! Glad to do it in New York.”
Williams’ quarterfinal opponent will be 11th-seeded Italian Flavia Pennetta, who opened Monday with a 7-5, 6-2 victory over 29th-seeded Aussie Casey Dellacqua on the hardcourts at the USTA Billie Jean King National Tennis Center.
The Italian has lost all five previous matches against Williams but will head into the clash with a positive attitude.
She said: “You just have to play your tennis and do your best. Of course, she’s better than me, but if I believe I can beat her, maybe if she doesn’t have a good day I can do that.
“If I get on the court and just play and try not to lose 6-0 6-0, I’m going to lose 6-0 6-0.”
32 year old, Pennetta played her best Grand Slam in New York, where she reached the quarterfinals now on five occasions, including a surprising run into the semifinals a year ago.