British number one Andy Murray was left to rue a missed opportunity as Novak Djokovic recovered from an early setback to move a step closer to the last four of the ATP World Tour Finals.
Murray began brightly at London's O2 Arena and edged the opening set, only for the top seed to restore parity in the second, meaning punters were struggling to decide how to bet as the game headed for a deciding set
Djokovic powered into a 4-2 lead in that decider before Murray hit back to move to within two points of victory at 5-4.
However, Djokovic showed why he is the top ranked player as he served his way out of trouble before breaking for the third time in the contest.
Murray looked set to take the match to the wire but failed to take advantage of two break points and Djokovic completed a thrilling 4-6 6-3 7-5 win. The Serbian is now 4-3 ahead in matches between the pair in 2012.
Tomas Berdych beat Jo-Wilfried Tsonga 7-5 3-6 6-1 in the other tie in Group A to leave all four players still in the hunt for the two semi-final places.
A straight-sets victory over Tsonga on Friday would guarantee Murray a last-four spot. The Scot will be keen to bounce back following Wednesday's defeat.
"The last two minutes of the match probably is what decided it. He broke from 15-40, and then I had 15-40 next game and didn't break. So that was the moment that decided the match," Murray told news sport reporters
"All the matches, especially the last few, have been extremely close and decided by a few points.
"The intensity of my matches with him this year have been extremely high. I think both of us have seen things in each other's game improve, and that's why there are a lot of long rallies."