Briton Joe Salisbury and American Rajeev Ram agonisingly missed out on the doubles final of the ATP Finals and the world number one ranking.
The pair led by a set and a break, and were 7-1 up in the match tie-break, but lost 6-7 (4-7) 6-3 11-9 to Edouard Roger-Vasselin and Jurgen Melzer.
Australian Open champions Salisbury and Ram also had a match point in the tie-break but were denied.
Salisbury, 28, was aiming to become the event’s first British doubles finalist.
Victory would have meant ending the year as the top pairing after a season featuring their maiden Grand Slam title together as well as a US Open semi-final and French Open quarter-final.
Salisbury had to self-isolate in the build-up to the tournament after his coach tested positive for coronavirus and said the pair “had not played very well” on their way to the last four.
“It’s tough losing that but I don’t really feel like we deserved to be in the final,” he said.
“It wasn’t a great quality tie-break. We were up a lot but they hit two double faults. Obviously, we should win from that point.”
Having won a tight first set, Salisbury and Ram broke in the first game of the second and were comfortable.
But Ram missed a simple volley on serve which would have given them a 3-1 lead and their opponents won five games in a row en route to winning the set.
The British-American pair dominated the early exchanges of the tie-break but France’s Roger-Vasselin and Austrian Melzer produced a remarkable comeback, sealing victory on their first match point when Melzer hit a winner between Ram and Salisbury at the net.
They will play Dutchman Wesley Koolhof and Croatia’s Nikola Mektic in Sunday’s final (15:30 GMT).