THE figure in white was instantly recognisable, but Novak Djokovic has been a pale shadow of himself in London this week.

The world No.1 slipped to another defeat in the Barclays ATP World Tour finals yesterday, as his fellow Serb, Janko Tipsarevic, inexorably moved to a 3-6, 6-3, 6-3 triumph in two hours, seven minutes.

The result was inevitable as soon as Djokovic lost the second set. He neither had the will nor the legs to prevail in a decisive set, though something inside him persevered and Tipsarevic had to work hard to gain his first victory over his friend.

Djokovic was also spared the toil of coming back to the O2 today to face Roger Federer in the first semi-final. That dubious honour falls to David Ferrer of Spain who lost his first match in the tournament last night. Tomas Berdych defeated the Spaniard 3-6, 7-5, 6- 1 and will play Jo Wilfried-Tsonga in the other semi-final.

The world No.1 thus plays no further part in the tourney and he may be quietly relieved.

A series of observations indicate that the O2 Arena has not witnessed the authentic Nole this week. He lost to Ferrer in straight sets, despite having an overwhelming winning record against the Spaniard. He slipped to defeat to Tipsarevic when the authentic Djokovic would surely have cruised away from his countryman as he has on the three previous occasions they have played.

Djokovic has also lost two matches out of three at the O2. Before London, he had lost four matches out of 73.

It was inevitable that the strains of an extraordinary season would tell on the 24-year-old. The signs were there when he retired hurt from a Davis Cup match against Juan Martin del Potro in September. They were flashing in neon lights when he was beaten by Kei Nishikori, ranked 25th in the world, in Basle early this month. He then retired in Paris before facing Jo-Wilfried Tsonga.

The Nole that embarked on the tour finals on the banks of the Thames was not, then, the invincible force that had captured the Australian Open, Wimbledon and the US Open this year. He was diminished in strength, pace and motivation. The fall-off was slight in all areas, but more than enough to leave him vulnerable to another top 10 player.

Asked what was missing from a game that dominated the sport for most of the year, Djokovic replied: “Freshness.” He later expanded his answer, saying that his will to win had been eroded and he was simply unable to give 100%. “I am not able to do that now because I have very little left,” he said.

He added: “There are those tournaments towards the end of the year when you don’t feel 100% fresh mentally, physically or emotionally.”

Djokovic said his body had suffered “overload”, adding: “It has just been too much this year. Mentally I feel drained as well. I just do not have that freshness in my mind for the matches and I do not have the dynamism that I had in 10 months of the year.”

Tipsarevic, at 27, has enjoyed an excellent year, rising from 49 to nine in the rankings and finding a place in the tour finals after the withdrawal of Andy Murray through injury. He, too, has had a long season, but he was energised by the prospect of playing in the tour finals and was candid in the assessment of his win.

He said: “Not trying to undermine my performance or my victory today, I can freely say that this was not Novak Djokovic from the US Open or Wimbledon, which is in a way normal. He has won everything a person can win. He has had the best season in the history of this sport. So it’s normal that he had some shoulder issues, whatever.

“But on the other hand, I saw him trying and fighting till the end. I’m giving credit to me because I managed to beat the world No. 1, maybe not on his best day. But still I feel that’s a victory that no one can take away from me.”

The crucial point for Tipsarevic came at the beginning of the second set, when he survived relentless Djokovic pressure on his serve. It was as if Djokovic was going for broke, trying to end the match quickly. Tipsarevic did not bend, however, and then broke his friend’s serve. The second set was won in a gruelling 53 minutes and the match tipped dramatically in favour of the world No.9.

Djokovic and Tipsarevic will soon meet again. “I’m going to the Maldives on Monday, hopefully with Novak. He’s going to come there on Thursday. I was telling you guys that we are close off court. I’m having dinner with the guy tomorrow, and I saw him this morning at breakfast,” he said.

The rest cannot come too soon for a drained Djokovic and a jubilant Tipsy, who can celebrate with the $265,000 he unexpectedly earned as a playing substitute at the O2.

It is now Federer v Ferrer and Tsonga v Berdych today. They are now the last men standing in a week when the O2 Arena has resembled a casualty station. The ultimate survivor will be rewarded with a winner’s prize of $1.6m.