Down but not out: Djokovic will have to beat fellow Serb Janko Tipsarevic to secure his place in the last four [GETTY]

Spain's David Ferrer stunned world number one Novak Djokovic to reach the ATP World Tour semi-finals on Wednesday, outplaying the Serb 6-3 6-1 at London’s O2 Arena.

Man-of-the-year Djokovic produced a lacklustre display against the world number five, crashing to defeat in one hour 15 minutes to leave his hopes of progress in doubt.

Djokovic, who edged past Tomas Berdych in his opening match, will now have to beat fellow Serb Janko Tipsarevic in his final Group A round-robin match on Friday to reach the semis.

Ferrer, the 2007 runner-up at the tournament, beat Andy Murray in straight sets in his opening match after which the Briton pulled out with a groin injury.

The Spaniard was inspired against Djokovic, taking complete control after breaking serve in the seventh game of the opening set.

Djokovic, winner of three of the year's four Grand Slams, made 33 unforced errors throughout the match and offered little resistance in the second set.

In the earlier game Tomas Berdych came within inches of a second consecutive defeat at the Tour Finals but rode his luck to beat Tipsarevic 2-6 6-3 7-6.

Tipsarevic ended the day with problems of his own after apparently hurting his knee towards the end of the match.

Source: Reuters