Novak Djokovic left himself needing a favour from David Ferrer to reach the semi-finals of the Barclays ATP World Tour Finals after a 3-6 6-3 6-3 loss to fellow Serb Janko Tipsarevic in his final group match today.
The world number one certainly played better than in his thrashing by Ferrer two days ago but he faded badly after winning the first set and will be going home unless the Spaniard beats Tomas Berdych tonight.
Bizarrely, in losing his match Djokovic may actually have increased his chances, with Ferrer now needing to beat Berdych to secure top spot in the group and therefore avoid hot favourite Roger Federer in the last four.
Djokovic described his performance against Ferrer as "terrible", and the 6-3 6-1 defeat left him with much work to do against close friend Tipsarevic.
The 27-year-old, a stand-in for Andy Murray, was already out of contention for a semi-final spot, but a first victory in four meetings with Djokovic would have provided a fine end to his best season.
However, it soon became clear this was more like the player who has dominated 2011 and Djokovic took control of the first set with a break in the fourth game.
He was moving well and hitting the ball much more crisply than he had on Wednesday, and Tipsarevic had to fight off two set points at 5-2 when the net twice came to his opponent's aid.
That earned Tipsarevic, one of the ATP Tour's most engaging figures, the support of the crowd and there was a loud cheer when he managed to hold, but Djokovic had no trouble serving it out.
The errors began to creep in at the start of the second set, though, and Tipsarevic capitalised in the sixth game when a Djokovic drop shot failed to clear the net.
The world number nine was trading blow for blow with his countryman but he could not cement the break as some amazing defence from Djokovic eventually drew the mistake from Tipsarevic.
Back came the underdog, Djokovic suddenly looking very weary, and this time he made no mistake, clinching the set at the second opportunity when the top seed sent a return well long.
That made the result of this match largely irrelevant - although not for Tipsarevic, of course - with a Berdych win later now guaranteed to send the Czech through, and Djokovic was broken again at the start of the decider.
The zip of the first set had gone out of the 24-year-old's shots and he quickly slipped three match points down on his own serve. He saved two but dumped a forehand into the net on the third to give Tipsarevic a first win at the World Tour finals.
The 27-year-old, who is going on holiday with Djokovic after the tournament, said: "I started the year ranked 49 and if anyone told me I would have finished it like this then I would have taken it in a heartbeat."