Top seed Novak Djokovic had to fight through the longest tiebreak of

his career on Monday while Roger Federer put on a post-midnight master

class as both players powered into the quarter-finals of the US Open.

Top

seed Djokovic began the second week as forecast rain held off by

defeating former tennis tyke Alexandr Dolgopolov of Ukraine, who grew

up on the ATP tour as the child of a coach, 7-6 (16-14) 6-4 6-2.

Federer

and Juan Monaco began at 11.50pm local time, the latest men’s start in

tournament history; the Swiss five-time champion wasting no time in a

6-1 6-2 6-0 win over the Argentinian lasting 65 minutes.

The first set took just 19 minutes with Federer off like a rocket, and serving four straight aces for a 2-0 lead in the second.

The

rest of the rout was a blur as the third seed got on and off court

under the threat of rain which did not arrive quite as forecast.

Federer

finished off his brilliant, if brief, evening, on his third match point

to advance in style with an untouchable winner to the corner.

“It was tough for Juan, he fought bravely,” said Federer, through to his 30 straight grand slam quarter-final.

“But it was my day tonight and it feels great.

“I’m very happy with how I played. It was a late start but we had to be ready for that.”

Djokovic,

chasing a third grand slam trophy this season, will next play good

friend and Davis Cup teammate Janko Tipsarevic after the Serb put out

Spanish veteran and 2003 finalist Juan Carlos Ferrero 7-5 6-7 (3-7) 7-5

6-2.

The dream ended for American eighth seed Mardy Fish as he

lost in more than three and a half hours to No.11 Jo-Wilfried Tsonga

6-4 6-7 (5-7) 3-6 6-4 6-2.

Tsonga will next face Federer after beating the Swiss at Wimbledon where the Frenchman had trailed two sets to love.

Djokovic admitted that the huge first-set tiebreaker determined the outcome of his match.

“It

took nearly half an hour. It was very important to win it. It had to be

the longest tiebreak I’ve ever played and it was a turning point,” he

said.

“After winning that one, there was a better performance from my side.”

Djokovic admitted that he was jittery as he played on the minor showcase Armstrong Court for the first time in years.

“The wind made for tricky conditions. My opponent knows how to play well in those conditions,” he said.

“I was a bit confused on the court at the start by his game.”

Djokovic finished with 13 winners in the demanding contest and will now get to face a close friend.

“At least one Serb will be in the semis, which is great for our country,” said Djokovic.

“I’ve never played Janko in a grand slam. But it’s a quarter-final and we both want to win.”