Andy Murray is considering adding another tournament to his schedule for the rest of the year as he looks to qualify for the season-ending Barclays ATP World Tour Finals in London.

The Scot dropped out of the world's top 10 for the first time in more than six years on Monday and needs to pick up points in the next six weeks to make it into the top eight in time for London in early November.

Murray's quarter-final defeat by Novak Djokovic at the US Open dropped him down to No.11 in the ATP rankings, his lowest position since June, 2008, with champion Marin Cilic and runner-up Kei Nishikori overtaking him.

And in the Race to London, which only applies to points won in 2014, Murray is also 11th, 355 points behind eighth position, currently occupied by Tomas Berdych. With two Masters 1000 events to come, in Shanghai and Paris, Murray has time to move himself up the standings.

But having initially ruled out the idea he could chase a London spot by committing himself to extra tournaments, sources close to Murray say he may now play two events before Shanghai. That would mean either an ATP 250 in Shenzhen, China, or the Malaysian Open, both of which start a week on Monday, followed by either an ATP 500 in Beijing or Tokyo the week before going to Shanghai.

A third victory in Shanghai would give him 1000 points, while 600 points go to a runner-up, points that would vastly improve his chances of qualifying for London again.

His former coach, Brad Gilbert, told reporters in New York that the way Murray played against Djokovic showed that he is on track to regain top form, a year after undergoing back surgery that led to him missing the final two months of 2013.

"From what I saw in those first two sets that's as good tennis as I have seen him play since he won Wimbledon in 2013 or here in 2012," Gilbert said. "I'm confident that a year from now he'll be back in the top three."