US Open: Andy Murray faces a tougher ride than Novak Djokovic

Andy Murray shows his frustration during his win over Denis Istomin (Getty Images)

On the basis of their form so far at the US Open it is no surprise that the bookmakers consider Novak Djokovic a better bet than Andy Murray to win the title next Monday. It is equally no surprise that Murray, who is seeded to meet Djokovic in the semi-finals, brushes aside talk of favourites.

"I always say that in tennis, and any individual sport, it doesn't really matter what happened two days ago," Murray said in the wake of his fourth-round victory over Denis Istomin, the world No 65. "You turn up on the day of the next match and you might feel awful. You never know. It doesn't matter how you've played up to this point. You can always get better – or get worse. I saw some of Novak's match today. It looked like he played extremely well. But the matches will get tougher now."

While Murray needed more than three hours to beat Istomin 6-7, 6-1, 6-4, 6-4, Djokovic took just 79 minutes to trounce the world No 43, Marcel Granollers, 6-3, 6-0, 6-0.

Djokovic, who dropped only four games in the previous round against Joao Sousa and has won all four of his matches in straight sets, will be strong favourite to win his quarter-final today against the world No 24, Mikhail Youzhny, who needed four hours to overcome Lleyton Hewitt.

Murray, who has dropped sets against Istomin and Leonardo Mayer, faces a significantly tougher quarter-final against Stanislas Wawrinka, the world No 10, who knocked out Tomas Berdych.

Wawrinka has long lived in the shadow of his fellow countryman Roger Federer, but at the present rate the 28-year-old could overtake his Swiss Davis Cup doubles partner in the rankings by the end of the year.

This is the first time that he has gone further in a Grand Slam tournament than Federer and it is by no means inconceivable that he could be the man to deny his friend a place in the season-ending Barclays ATP World Tour Finals in London.

This has been the best year of Wawrinka's career. He has played in four finals, winning one, reached the quarter-finals at the French Open and went closer to denying Djokovic the Australian Open title than anyone, losing a five-hour marathon after the world No 1 won the fifth set 12-10.

"I'm really happy with my year and what I'm doing right now, but I would prefer to still have Roger playing in the tournament," Wawrinka said. "I watched his match [against Tommy Robredo] 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."

Murray has won eight of his 13 meetings with Wawrinka, but honours are even at Flushing Meadows. Murray won in three sets in the third round in 2008 but Wawrinka won in four sets in the fourth round two years later. That was the last occasion when Murray failed to reach the quarter-finals or better of a Grand Slam event, apart from this year's French Open, which he missed through injury.

"I didn't play particularly well," Murray said of the 2010 meeting in Louis Armstrong Stadium. "I struggled on that court, so I don't have particularly good memories from that match. I did go away from that match a bit down. It was a tough loss for me for sure. But I also played him in Arthur Ashe Stadium in a night match and played really well, so I've had an interesting mix against him.

"I'll need to play a good match. I think he's improved quite a bit this year. Some of the things he didn't do so well before he's improved, so he has fewer weaknesses. He's more experienced now. 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.

"Hopefully, I'll start playing a little bit better from now on. Sometimes I've played very well in the first week of a Slam. Sometimes you maybe feel like there's a little bit of something to lose. But I'm in the quarter-finals of a Slam. It's not an easy thing to do and the matches are going to get tougher. I'll have to up my game."