JOIN USOn the final day of round-robin action at the O2 Arena a jaded Djokovic was beaten 3-6, 6-3, 6-3 to end Group A with two defeats and one victory.
Djokovic would still have crept into the semifinals through the back door had David Ferrer beaten Tomas Berdych later but the Spaniard went down 3-6, 7-5, 6-1.
After staring elimination in the face Berdych ended up winning Group A and thus avoided a semifinal against holder and red hot favourite Roger Federer. The Czech will take on Jo-Wilfried Tsonga, the charismatic Frenchman who sent Nadal packing on Thursday, in the semifinal while Ferrer's punishment for letting Berdych off the hook is a clash with the unbeaten Federer.
Djokovic's exit means three of the world's top four failed to survive the group stage although in Murray's case he withdrew after one match here because of a groin injury.
Tipsarevic, who replaced Briton Murray, walked off with earnings of $190,000 after finishing his year with a first ever victory over close friend Djokovic -- $70,000 as his fee for being the on-site alternate and $120,000 for his sole win. While he was delighted with his victory, Tipsarevic admitted his opponent, winner of three of the year's four Grand Slam titles, was not firing on all cylinders.
"I'm not trying to undermine my performance or my victory today, but I can freely say that this was not Novak Djokovic from the US Open or Wimbledon," he said.
“My body says that it's overload,” Djokovic, who ended the year with a 70-6 record after his first back-to-back defeats since March 2010, told reporters.