Andy Murray has slipped out of the world's top 10 for the first time since 2008 following Marin Cilic's victory over Kei Nishikori in the final of the US Open.

Murray's new ranking of 11 means he faces a battle to secure one of the eight slots available for the end-of-season World Tour Finals in London in November.

He has a significant number of points to make up on Tomas Berdych, who occupies the final qualifying position.

The 27-year-old Scot lost to Novak Djokovic in the quarter-finals in New York. He is due to play three more events before the London tournament and he may need to reach the final of either the Shanghai or Paris Masters to have a decent chance of qualifying.

Murray has fallen from three to 11 in the rankings since having back surgery in September 2013, two months after winning Wimbledon.

Since his operation, he had not beaten a top-10 player until overcoming Jo-Wilfried Tsonga in the fourth round at Flushing Meadows. At this year's other three Grand Slam events, Murray reached the last eight at the Australian Open and Wimbledon, while he was beaten at the semi-final stage of the French Open.

Cilic overwhelmed Japanese star Nishikori 6-3, 6-3 6-3, carrying the momentum from his semi-final victory over Roger Federer and turning it into major silverware and a £3million cheque. The Croatian said: "It seems completely unreal to be called a Grand Slam champion.

"I have dreamed about this all my life and then suddenly, over the last four or five days, everything started to change.

"It means everything. It's a huge accomplishment and huge moment for myself and for my team and for everybody around me who was with me all these years supporting me, believing in me and never giving up. This is just the peak of the world."

It was the first slam final in almost 10 years not to feature Federer, Djokovic, Rafael Nadal or Murray and the first between two first-time finalists ranked outside the top 10 since Pat Rafter beat Greg Rusedski in the US Open final in 1997.