Great Britain's Andy Murray has revealed that he does not expect to finish top of the world rankings by the end of the year.
Victory in the upcoming Shanghai Masters and the end of season ATP World Tour event would give the world number three a chance of reaching the summit.
However, US Open champion Murray believes that only Novak Djokovic has a realistic chance of overhauling current number one Roger Federer.
"It will be very difficult to finish the year as number one," he said. "I think Novak is too far off and guaranteed that.
"I will keep working hard and focus for the rest of the year and hopefully have a chance next year."
Murray will head into the tournament in Shanghai as the defending champion.
