Fifth seed Elena Dementieva cools down during her quarter-final match with Switzerland's Patty Schnyder

Schnyder is in the last eight at Flushing Meadows for the first time since 1998 but faces an uphill struggle against the Russian

Dementieva runs away with the first set and holds off a Schnyder fightback to book her place in the semi-finals

Novak Djokovic is out of sorts in the first set of his match against Tommy Robredo and shows his frustration by throwing his racquet

Djokovic needs treatment on thigh and back injuries but he is soon in control of the match after taking the next two sets

Robredo looks capable of causing a major shock when he levels at two sets all

But Djokovic regains his composure and eventually comes through 4-6 6-2 6-3 5-7 6-3 to reach the last eight

Defending champion Roger Federer begins his fourth-round clash against Igor Andreev in uncertain fashion

The early frustration for Andreev is that he cannot capitalise on an immediate break of serve and needs a tie-break to win the first set

Federer is hanging on early in the second set and is a relieved man to level it in another tie-break

But after winning the third set, Federer is broken midway through the fourth as Andreev battles back

After slipping 4-2 down in the decider Andreev is infuriated to let four break-back points slip away

Federer eventually seals victory after three hours 32 minutes of nailbiting action

What started as an afternoon match between Federer and Andreev ends as part of the night session

Federer goes on to face Gilles Muller after the qualifier from Luxembourg sees off fifth seed Nikolay Davydenko in four sets

Jelena Jankovic makes friends on Louis Armstrong Stadium after beating Sybille Bammer 6-1 6-4

American hope Andy Roddick makes a blistering start to his night session match against Fernando Gonzalez

Roddick's fiancee Brooklyn Decker watches intently from the stands on Arthur Ashe Stadium

Chilean Gonzalez cannot contain the rampant Roddick and quickly slips two sets behind

Actress Cameron Diaz (right) is among those enjoying Roddick's impressive performance

Roddick seals a swift 6-2 6-4 6-1 victory in just 87 minutes