US Open Round-up: Djokovic through

There was an old-fashioned fight at the US Open on Thursday but not the one tournament officials wanted to see.

Instead of happening on the court, the scuffle broke out in the upper deck, high above Arthur Ashe Stadium where Novak Djokovic and Philipp Petzschner were locked in their own battle.

Play stopped briefly as New York police handcuffed three rowdy fans and evicted them from Flushing Meadows.

The fracas in the stands came at the end of a day when some of the sport's heavyweights delighted in humbling lesser-known opponents in second round matches.

Each of the five featured matches on centre court were decided in straight-sets. At times the quality of tennis was breathtaking and the crowds roared their approval, but it was rarely a fair contest.

Roger Federer's victim was Germany's Andreas Beck. He won the match 6-3 6-4 6-3 in one hour 41 minutes and even the Swiss master himself was impressed.

'It's the perfect start,' he said. 'I played Monday, had two days off. I had another easy one physically today, and here I am in the third round feeling like I'm completely in the tournament.'

Maria Sharapova was also in a hurry, belting Czech Iveta Benesova 6-1 6-2, but neither of the former champions could match the ruthless display from Caroline Wozniacki.

The Dane needed just 47 minutes to inflict the dreaded 6-0 6-0 'double bagel' on Taiwan's Chang Kai-chen and remain on course for a meeting with Russian Sharapova in the fourth round.

Russia's Vera Zvonareva, Wimbledon finalist this year, and Belgium's Yanina Wickmayer, semi-finalist at the US Open last season, also registered easy wins on another steamy day when the Extreme Weather Policy was invoked as temperatures climbed past 91 degrees Fahrenheit (33 Celsius).

A year ago, Kim Clijsters was the mom hogging the spotlight at the US Open. This time it is Mother Nature.

Unrelenting heat and swirling winds have transformed the last grand slam of the year into a battle against the elements and now Hurricane Earl is approaching New York, threatening to dump gallons of rain on the city that never sleeps.

Petzschner landed a few blows on Djokovic but the world number three was way too crafty for the German, winning 7-5 6-3 7-6 to meet James Blake in the next round.

Djokovic's fellow Serb Jelena Jankovic, the women's fourth seed, survived after being pushed to three sets by Mirjana Lucic.

Russian Nikolay Davydenko, however, was left punch-drunk after being hammered 6-3 6-4 6-2 by Frenchman Richard Gasquet.

'I don't know if I need to have a coach, a mental coach or if I need to go somewhere to change my brain,' the sixth seed said.

The casualty rate among the seeds in the first four days of the championship has been almost as brutal as the baking heat with 22 making early exits, including six more Thursday.

Agnieszka Radwanska, Aravane Rezai and Maria Jose Martinez Sanchez were sent tumbling out of the women's draw.

Davydenko was the highest men's seed to fall and was joined at the exit by Thomaz Bellucci and Croatia's 11th seed Marin Cilic, upset 5-7 7-6 3-6 7-6 6-1 by Japan's Kei Nishikori.

For Federer it was business as usual in his pursuit of a 17th grand slam title but there was no repeat of the magical between-the-legs trick shot he played in his opening match.

'Tougher matches will only be coming up now, I guess,' he said.

'It's gonna be interesting to see how the Saturday conditions are going to be with the hurricane sort of moving in. We'll see how that goes.'

Djokovic produced a stunning backhand winner on Thursday that would make it on anyone's highlights reel but said he had no plans to try and replicate Federer's shot.

'I have something else between my legs,' he told the centre court crowd.

Wozniacki is looming as the favourite to win her first grand slam title after a flawless start to the tournament.

Promoted to top seed after world number one Serena Williams withdrew with a foot injury, Wozniacki won three lead-up tournaments and has carried her form into the U.S. Open.

'When you're winning, you have that confidence,' she said. 'You go out on the court and you know what to do. You're in your own bubble. That's what I'm aiming for.'