There was no shortage of drama in the most eagerly-awaited clash of the group stages at the Barclays ATP World Tour Finals but it was Novak Djokovic who edged out Andy Murray to put himself in the driving seat in Group A.
There is still all to play for in the final matches on Friday, though, after Tomas Berdych beat Jo-Wilfried Tsonga 7-5 3-6 6-1 in the evening match.
The result means none of the players are yet through or eliminated, although Djokovic only needs a set against Berdych while a straight-sets win for Murray over Tsonga would be enough for the third seed.
It was the seventh meeting between Murray and Djokovic this season and their rivalry is fast developing into the headline act on the ATP Tour.
They were tied at three all, with Djokovic winning epic clashes at the Australian Open and in their last meeting in Shanghai a month ago but Murray coming out in top at the Olympics and, most notably, to win his first grand slam title at the US Open.
The Scot could not have started better here and played a near faultless first set but he could not sustain it and in the end a third-set comeback counted for nothing as Djokovic prevailed 4-6 6-3 7-5 in two hours and 34 minutes at London's O2 Arena.
This clash will not live long in the memory for the quality, first set from Murray aside, but it was somehow inevitable it would go down to the wire.
Assessing his rivalry with the man he first played as a junior more than a decade ago, the 25-year-old said: "I think both of us probably see each other's games pretty well. Especially this year, because we've played so much.
"You kind of know a little bit what to expect. I think that's why all the matches, especially the last few, have been so close and decided by a few points. The intensity of my matches with him have been extremely high this year.
"But the one thing I would say is this year I think both of us probably have seen things in each other's games improve and that's why there's a lot of long rallies and the matches are incredibly tight."
Murray was blistering in the first set, pushing Djokovic back with the ferocity of his forehand and dropping only three points on serve after breaking in the opening game following the kind of ding-dong rally for which the pair have become famous.
He was still in the ascendancy at the start of the second and had a chance in the third game only for Djokovic to find the corner with a drive volley.
Three games later the Serb created his first opening and took it when Murray chose to serve and volley and just missed the baseline.
"There are decisions you make in matches," he said afterwards. "If they come off, you get told you're a genius. If you miss them, then you're an idiot. That was just one of those ones that didn't work today."
The momentum was with the world number one and he looked in total control in the decider when he twice had chances for a double break.
But Murray dug in and pulled back to 4-4 only for Djokovic to break again and then save two more break points to serve it out.
"In about the last two minutes of the match probably is what decided it," said the Scot. "He broke from 15-40 and then I had 15-40 in the next game and didn't break."
Djokovic was fully prepared for a battle, and he said: "It was another great match, another great performance from both of us. I hope that people who watched it agree with my opinion.
"I didn't expect anything less other than a tough match that went down the wire and was decided on the last point.
"It was important for me after dropping the first set to stay mentally tough and believe that I can get my opportunities, and when they're presented to try to step in and use them. That's what I've done."
The round-robin format has led to complicated scenarios in the past, most notably in 2009 when Murray was eliminated by a game, but Berdych insisted he will pay no attention to that side of it.
The Czech, who registered his first win in London this year today after first-round losses at Wimbledon and the Olympics, said: "I don't like mathematics at all. I will try to play tennis and that's it."