Andy Murray was left in the shade by Juan Martin del Potro this year as the gangly Argentine made his grand slam breakthrough although the Briton is confident his time will arrive soon.

Del Potro, at 21 a year younger than Murray, stunned Rafael Nadal and then Roger Federer to win the US Open in September meaning Murray is now the odd one out - the only member of the world's top five without a major title on his CV.

He gets a chance to prove his credentials in London over the next week when he competes for the one million pounds ($1.65 million) jackpot at the ATP World Tour Finals and believes winning the tournament is the next best thing to a grand slam.

"This tournament is just behind the grand slams because you have to win five matches, or four matches, against the top players in the world," Murray, who starts his round-robin matches against Del Potro today, told reporters.

"You might even have to beat the number one or number two in the world twice to win the event so it's not quite the same as a grand slam but it's a huge, huge tournament."

Murray has grown tired of fielding questions about his failure to win a grand slam this season.

He pointed out he equalled his best run at the Australian Open and went further than ever before at Roland Garros and Wimbledon, reaching the quarter-finals and semis respectively.

"Everyone views it a little bit differently but I still believe that I have a few chances, maybe one or two more chances, to win a grand slam," said Murray who claimed his sixth title of the year in Valencia earlier this month.