US Open 2013: Stanislas Wawrinka issues warning to Andy Murray ahead of quarter-final

The Swiss claims to be in the form of his life

Stanislas Wawrinka has warned Andy Murray he is in the form of his life as they prepare to meet in the quarter-finals of the US Open.

The pair are good friends and often practise together so there will be no secrets, but Wawrinka hopes he can surprise Murray with the quality of his play.

The Swiss has returned to the top 10 this summer for the first time since 2008 and stunned fifth seed Tomas Berdych in the fourth round.

Murray may be slightly relieved he does not have to face Berdych, who he has a losing record against, but he has not had an easy time against Wawrinka either.

The Scot leads their head to head 8-5 but his last early loss at a grand slam came against Wawrinka here in the third round in 2010, while the world number 10 lost just three games in beating Murray in their most recent meeting on clay in Monte Carlo this spring.

This year Wawrinka has shown more consistency and produced some stunning displays, none better than in the epic match he played against Novak Djokovic in the fourth round at the Australian Open, which he lost 12-10 in the fifth set.

Wawrinka highlighted the title he won in Portugal in May as a key moment and said of his improved form: "It's confidence, for sure.

"I had a tough beginning of the year but at the same time it was really positive for me because I was playing great tennis.

"This is for sure my best year. I think I'm playing my best tennis ever.

"Andy is a really good player. It's always a tough match, 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."

Murray has not hit top form yet and knows he will need to play a better match than he did against Denis Istomin in the fourth round.

He said of Wawrinka: "He's improved this year quite a bit.

"He has a very good backhand. He serves well. He's solid up at the net. He makes a lot of returns. He makes it very tricky for you. He's a top player. It will be a very tough match for me."

Wawrinka, meanwhile, is in the unusual position of being the last Swiss player left after Roger Federer's shock loss to Tommy Robredo.

It is not something he wants to get used to, and he said: "I'm really happy with my year but I would prefer to have him still playing in the tournament.

"I watched his match and it was not that good. I was sad for him, because he's a good friend and I like it when he's winning grand slam titles. I hope he will come back stronger."

Today's other quarter-final pits Novak Djokovic, the only man yet to drop a set, against Russia's Mikhail Youzhny.

PA