Novak Djokovic faces a nervous wait to discover if his season has come to a disappointing end at the ATP World Tour Finals after the World No 1 lost 3-6, 6-3, 6-3 to Janko Tipsarevic on Friday.
Djokovic has lost two of his three Group A matches in the season finale at London's O2 Arena, but he will still qualify for the semi-finals if David Ferrer beats Tomas Berdych in last night's late match, while a Berdych victory would eliminate the Serb.
After a magnificent season that brought Djokovic three Grand Slam titles, five Masters crowns and top spot in the world rankings, the 24-year-old has finally run out of steam this week.He arrived in London on an incredible run of 69 wins from 73 matches, but that record has been slightly tarnished by two successive defeats here.
Djokovic's lacklustre loss against Ferrer on Wednesday had taken his tournament fate out of his hands and his season could be over after he allowed a one-set lead to disappear against fellow Serb Tipsarevic.
"There were a lot of ups and down from both Novak and me, but I am very happy to be here after starting this year at 49 in the world," Tipsarevic said. "I generally do not like to play my fellow countrymen, but even during the match I felt proud just to see the two Serbia flags in the O2 Arena."
Djokovic admitted after the Ferrer defeat that he was not operating at 100 per cent after such a long season and his stamina reserves reached breaking point as Tipsarevic won a 12-minute game to open the second set.
"I just wasn't there. It was the worst match I've played this season. So many unforced errors. I'm not playing well. Maybe it's because of the length of the season," Dkokovic had said after the defeat to Ferrer on Thursday.