Twin challenges for Federer at US Open

New York:

Sleeping patterns are vital to top tennis players, so new father of twins Roger Federer knows he has his work cut out as he bids to become the first man in 84 years to win six straight US Opens.

Federer kept his campaign to match Bill Tilden on track on Saturday with a 4-6, 6-3, 7-5, 6-4 third-round win over old foe Lleyton Hewitt, also a father, and then took the time out to reflect on his new paternal responsibilities.

"We have a good setup. Mirka is great. She works extremely hard," Federer said of his wife, who gave birth to twin girls in July shortly after Wimbledon when her husband became the all-time Grand Slam title record holder with 15.

"She's tired during the day but she has also some help, has a little bit of life, and also can come and watch me play and get outside a little bit. That's important," Federer said.

"Sure, I'm losing sleep, but that's part of it. I make sure on my off day maybe I do get a night where I can sleep in longer or take an afternoon nap. It's working out OK."

Early on against Hewitt, it seemed as though Federer might be short of sleep as he gave an unusually listless first set display against the Australian livewire.

The match, rare in Federer's case, had been scheduled first up on the Arthur Ashe Stadium court and the midday sun was beating down as Federer looked for answers to his predicament.

He eventually found them, gradually finding his form and feet as the game went on and he later insisted that early start had not been a problem for him.

"We always practice at 11:00. Normally it's a time players really like to practice," he said.

"Sure, for a match it's rather on the earlier side, but I'd rather play 11:00 than 10:00 p.m., to be quite honest.

"But anything is fine. I think as a tennis player you have to be flexible, because you never know if we have rain or whatever it is, we're accustomed to being quite open when it comes down to scheduling.

"No, I don't think the first set was down to that at all. I was up 4-2, 40-love, so my start was actually OK."

If his start was OK, his end was even better as Hewitt's game began to unravel in the face of increased pressure from the world No.1 and in the end the Swiss star finished with a flourish.

"The way I came through, I was very happy, because I knew that being down a set against Lleyton is always going to be a difficult situation for me to be in," he said.

"Make one more mistake and I'm in the fifth set maybe, or I go down completely. So I was relieved coming through."