Andy Murray, the defending champion, believes he must " up his game" after overcoming Denis Istomin's power tennis and a blustery centre court to earn a 6-7,6-1,6-4,6-4 victory and move into the US Open quarter-finals where he will face ninth seed Stanislas Wawrinka.
Wawrinka, with the departure of Roger Federer, is Switzerland's only hope for Grand Slam glory here in New York after he beat fifth seed Tomas Berdych 3-6 6-1 7-6(6) 6-2 in two hours and 47 minutes to earn his time in the limelight.
Murray leads the head to heads with Wawrinka 8-5 and this will be their third meeting at the US Open with the British No1 winning in 2008 but losing in four sets to the Swiss player in 2010. Their first clash came in the Davis Cup on clay eight years ago and in their most recent clash - in Monte Carlo - Wawrinka easily accounted for the World No3 6-1,6-2 on clay.
Murray insisted he was never in danger against Istomin who tried three shots between his legs - winning just one point when the Scot missed an easy overhead. He said; " I was struggling a bit with the timing because of the wind but it made for some fun points. Today was tough and tricky, and I am just glad I got through in the end. Hopefully, I will start playing a little bit better from now on.
"I am in the quarter-finals of a Slam again and that's not an easy thing to do . The matches are going to get tougher and I will have to up my game.
"Stan has played great tennis all year and is very talented. He's improved this year quite a bit and so he has less weaknesses. He's a top player and it will be a very tough match for me.
Wawrinka believes he is playing the best tennis of his career and is eager to test his new found confidence against Murray, who is a regular practise partner on the circuit.
Wawrinka, who has gone further than Federer in a Slam for the first time, said;" For sure this is my best year and I think I play my best tennis ever. I think winning the title in Portugal against David Ferrer helped me to take my confidence to the next level.
"Andy and I have had some great battle when we play each other. It's always usually some tough matches, but I like to play him - I like his game. I think if I start well, if I stay with him, I can have a good chance to do something against him.
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"I will prefer to have Roger still playing in the tournament. I was sad for him, because he's a good friend and I like when he's winning Grand Slam titles."
In the women's event, top seed Serena Williams hammered 18th-seeded Carla Suarez Navarro of Spain 6-0,6-0 and now faces No. 5 seed Li Na, the first Chinese player to reach U.S. Open semi-final.
