Del Potro - Murray a step up

Juan Martin Del Potro admits he will have to find a few extra gears if he is to overcome Andy Murray in the quarter-final of the Madrid Open on Friday evening.

The Argentinean, ranked just two places below world number three Murray, has only failed to reach the last eight once duirng his nine tournaments this season.

But the 20-year-old accepts Murray, who has picked up three titles already in 2009, is playing a different level of tennis.

"The difference is big," said Del Potro. "I need to work hard to close the difference but I don't know if I can do that this year or next year."

Birthday boy Murray turns 22 on Friday and enjoyed an early present last week when he became the first British player to enter the top three of the world rankings, climbing above Novak Djokovic.

Great season

"I'm having a great season but I think Andy is much better than me at this moment," added Del Potro.

"He's won two or three Masters Series titles and right now he can beat any player on any surface. I hope to be like him soon."

Their only previous meeting on clay came at the 2008 Rome Masters, an ill-tempered encounter that will be best remembered for a verbal confrontation between the two players, when Murray claimed Del Potro had insulted his mother.

Del Potro, who retired in that match with a back injury in the deciding third set, said that for him the incident was now in the past.

"I'm okay with him, we have a good relationship," he continued. "We've known each other since we were 12, 13 and we've played many times and tomorrow is another time, and I hope to get my first win.

"That was the past, now we are older. He's number three in the world, I'm number five and we are both professionals. That was the past, and that's it.

"I hope to beat him the first time tomorrow. I hope to be in good shape and do my best to beat the number three."

Confidence

Murray progressed through to the quarter-final in the Spanish capital with an impressive 7-5 6-1 win over Tommy Robredo.

That was a huge confidence boost for the British number one but he knows Del Potro could be another big challenge for him.

"I think he's number five in the world right now, so he's obviously playing very well," said Murray.

"He's starting to play better on clay even though he was obviously brought up playing on it.

"Because of his height and because of his game style he's played better on hard courts but he's a tough player on all courts."