Nadal: Murray has potential to be number one

World number one Rafael Nadal believes Andy Murray will be “very difficult to stop” if he succeeds in getting his claycourt game up to the level he desires.

Murray, who later today plays Tommy Robredo in the third round of the Madrid Open, this week climbed into the world’s top three – a feat based largely on his performances on hard courts, where he has won all 11 of his titles to date.