Andy Murray survived a stifling New York day to reach the fourth round of the US Open but it is two different British players who will take centre stage tonight.

Murray admitted he struggled with his breathing in very humid conditions as he defeated Germany's Florian Mayer 7-6 (7/2) 6-2 6-2.

The defending champion made a sluggish start but never looked in any real trouble, aside from coping with the energy-sapping humidity.

Murray said: ''It was tough conditions. It was very, very humid. With the way that he plays, it was a tough match, especially the beginning.

''But I started the second set well. I started hitting the ball a little bit cleaner, was more aggressive after that, and finished it well.

''I was struggling breathing for most of the match.''

The Scot will face Uzbekistan's Denis Istomin tomorrow for a place in the quarter-finals, but other British interest has not ended with the exit on Saturday of Dan Evans.

Tonight, Colin Fleming and Jonny Marray will take on all-conquering twins Bob and Mike Bryan in the quarter-finals of the men's doubles in the night session on Arthur Ashe.

It will be a first grand slam quarter-final together for the Anglo-Scottish pair and a rare opportunity to play on the main court at a major.

Marray, of course, has experience of that on Wimbledon's Centre Court from his stunning run to the title with Dane Freddie Nielsen last year.

They beat the Bryans in the semi-finals, and the Yorkshireman has his sights set on a repeat.

Marray said: "We can't wait. To get the opportunity to play out there, not many people get that, especially against the Bryans as well.

"Obviously it can do nothing but give me some confidence knowing that I've been in a big match against them at a grand slam and come through with a win.

"It's on their turf this time but I'm sure it'll be a great occasion for both of us and hopefully we'll go out and play some good tennis."

At 35, the Bryans have had the best year of their career and are bidding for a calendar Grand Slam.

Fleming added: "Hopefully we can ruin their dream year. That's obviously our aim. But all credit to them, they're an amazing team and it's an amazing year and careers they've had so far."

Jamie Murray is also through to the quarter-finals after he and Australian partner John Peers defeated Americans Rajeev Ram and Brian Baker in a deciding tie-break.

In the most eagerly-anticipated match of the US Open so far, Serena Williams avenged her Australian Open defeat by beating young pretender Sloane Stephens.

Third seed Agnieszka Radwanska crashed out, though, losing to Russia's Ekaterina Makarova, while men's top seed Novak Djokovic crushed Joao Sousa.

Later today, second seed Victoria Azarenka and former world number one Ana Ivanovic clash while the men's fourth round begins with Roger Federer meeting Evans' conqueror Tommy Robredo and Rafael Nadal facing Philipp Kohlschreiber.