Feliciano Lopez makes a fantastic start in the final match of the day against world number one Roger Federer

Federer is in trouble at a set down and on serve deep into the second set against Lopez

But the world number one turns the match around with some breathtaking play to win four sets

Sixth seed Anna Chakvetadze takes the spotlight in the first of Monday's night matches, beating Tamira Paszek 6-1 7-5

Earlier in the day, fourth seed Svetlana Kuznetsova races through the first set of her match with Victoria Azarenka

Teenager Azarenka beat Martina Hingis in the last round but has no answer against Kuznetsova

Fifth seed Andy Roddick saves a set point to win the first set against Tomas Berdych

Berdych goes 2-0 down in the second set and then retires with sickness, sending Roddick through to the last eight

Britain's Daniel Cox loses in straight sets to 11th seed Thomas Fabbiano in the boys' singles

But there is better news for another British junior, Dan Evans, who wins his first-round boys' match

Teenager Agnes Szavay, playing her first US Open, faces Julia Vakulenko in the fourth round

Hungarian Szavay wins in straight sets to reach her first Grand Slam quarter-final

Israeli Shahar Peer reaches the last eight with a 6-4 6-1 win over Maria Sharapova's conqueror Agnieszka Radwanska

Tenth seed Tommy Haas looks to be in trouble when he goes a set and a break down against James Blake

But it is sixth seed Blake's turn to feel the heat when he lets Haas back in to level the match at one set all

Haas eventually edges Blake in a thrilling final-set tie-break to take his place in the last eight