Below-par Federer overhauls Hewitt while Djokovic also struggles

ROGER Federer captured his 14th consecutive win over Lleyton Hewitt to book his place in the fourth round of the US Open - but was forced to work by the Australian. 

WORK TO DO: Roger Federer makes an uncharacteristic 59 unforced errors against former world number one Lleyton Hewitt (Getty Images)

The duo lined up for the 23rd encounter - only four pairs have faced eachother more - with Hewitt's last win dating back to a Davis Cup meeting in 2003.

But 2003 champion Andy Roddick slumped to a 7-6 (3), 6-3, 3-6, 5-7, 7-6 (5) defeat to unseeded fellow American Isner in a thriller lasting just over four hours.

Former world number one Hewitt looked determined to break his miserable run against the Swiss and took the opening set before Federer hit back to wrap up a 4-6, 6-3, 7-5, 6-4 victory.    

Hewitt, seeded 31st, was typically aggressive as the pair took to the Arthut Ashes Stadium and Federer committed 23 unforced errors on the way to dropping his first set of the tournament.  

That sparked the 15-time grand slam winner - targetting his sixth consecutive title in New York - into action and Federer duly closed out the second set.

But Hewitt is not one to lie down without a fight and Federer was forced to save four break points in the fourth game of the third set to level at 2-2 before the Swiss player finally began to find some rhythm.

And despite being below-par, committing an uncharacteristic 59 errors, Federer was not to lose from that position and closed out the final set with a minimum of fuss.

The 28-year-old will now face America's James Blake or Spain's 14th seed Tommy Robredo in the last 16.

Roddick became the first big-name casualty of the men's draw as the 2009 Wimbledon finalist met his match after an inspired performance from Isner.

Meanwhile, fourth seed Novak Djokovic survived a scare against world number 276 Jesse Witten after dropping the first set.

Djokovic fought back in the second but Witten, in his debut grand slam appearance, came close to taking a 2-1 advantage, forcing a tie-break in the third.

But Djokovic - runner-up at Flushing Meadows in 2007 - prevailed and went on to close out the match 6-7, 6-3, 7-6, 6-4.