Djokovic storms into last eight

Novak Djokovic didn't let Philipp Kohlschreiber stand in the way of another Grand Slam quarter-final berth on Monday, reaching the US Open last eight with a straight-sets win over the German.

Serbia's world number one defeated Kohlschreiber 6-1, 7-5, 6-4 on another muggy day at Flushing Meadows, reaching the last eight at the US Open for the eighth straight year.

Meanwhile, second-seeded Federer on Sunday, came back from a set down to defeat Granollers 4-6, 6-1, 6-1, 6-1 by racing away with 20 of the last 24 games of the match which had been interrupted due to rain and the threat of lightning.

Federer, bidding to become the oldest Grand Slam champion in more than 40 years, clinched his 70th win at the tournament on the back of 57 winners and 13 aces.

But the 33-year-old had struggled in the first set where he slipped to 2-5 down against the world number 42 before he grasped welcome respite in the locker room to sit out the storm.

Federer will face Roberto Bautista Agut for a place in the quarter-finals after the 26-year-old Spaniard beat France's Adrian Mannarino 7-5, 6-2, 6-3.

Gilles Simon sent Spanish fourth seed Ferrer crashing to his earliest US Open defeat in five years with a 6-3, 3-6, 6-1, 6-3 third round win.

The 26th seeded Simon capitalised on the 52 unforced errors of the 32-year-old Ferrer, a semi-finalist in 2007 and 2012, who appeared to struggle physically towards the end.

Simon goes on to face Marin Cilic of Croatia, who beat South Africa's Kevin Anderson 6-3, 3-6, 6-3, 6-4, for a place in the quarter-finals.

Czech sixth seed Tomas Berdych, a semi-finalist in 2012, beat Georgian-born Russian Teymuraz Gabashvili 6-3, 6-2, 6-4 and next plays Dominic Thiem of Austria, the youngest player in the top 50 at just 20.

Thiem, who turns 21 on Wednesday, reached his first Grand Slam last-16 with an impressive 6-4, 6-2, 6-3 win over left-handed serve-and-volleyer Feliciano Lopez of Spain who is 12 years his senior.

Gael Monfils celebrated his 28th birthday a day early by sweeping past French Davis Cup teammate Richard Gasquet, the 12th seed, 6-4, 6-2, 6-2.

He will face Bulgarian seventh seed Grigor Dimitrov who saw off Belgium's David Goffin, 0-6, 6-3, 6-4, 6-1.