David Nalbandian came from two sets down to beat Roger Federer in an epic Masters Cup final and end the world number one's long winning streak.
Federer had won his last 35 matches and 24 finals, but only a fourth defeat of the season in Shanghai ended his hopes of a third successive Masters title.
The world number one took the first two sets on tie-breaks but Nalbandian hit back to take the third and fourth sets.
He led 4-0 in the fifth before finally winning an epic 6-7 6-7 6-2 6-1 7-6.
Federer had won 24 consecutive finals, an Open era record dating back to October 2003.
His last loss in a final came to Jiri Novak in Gstaad on 13 July, 2003, while defeat denied him a share of John McEnroe's professional-era winning record for a season of 82-3 set in 1984.
LONGEST WIN STREAKS SINCE '68
46 matches: G Vilas (July-Sept 1977)
44 I Lendl (Sept 81-Feb 82)
42 J McEnroe (Jan-May 84)
38 B Borg (Oct 79-April 80)
35 B Borg (May-Aug 78), T Muster (Apr-June 95), R Federer (June-Nov 2005)
B Borg (May-Aug 79),
31 I Lendl (Aug-Nov 85)
Federer won a titanic second set tie-break 13-11 but appeared to be on the ropes after being broken twice in the third set and seeing Nalbandian race through the fourth.
The Swiss champion dropped his serve twice to fall 0-4 down in the decider, but staged a remarkable comeback to twice break back and level it at 4-4.
He then broke Nalbandian at 5-5 to serve for the match, only for the Argentine to break back and force a tie-break.
Nalbandian appeared to have blown his chance when he pushed an easy backhand volley wide at 4-2 up.
But he held his nerve to take it 7-3, converting his first match point after four hours and 33 minutes as Federer found the net.
An exhausted Nalbandian, the world number 12, collapsed to the floor as he celebrated his first major tournament victory - his second title this year and only the fourth of his career.
And reflecting on his success, he said: "I surprised the world. He (Federer) almost never loses.
"To come back from two sets down against the world number one, with his record, it is just incredible."
As he picked up the winners' cheque for $1.4m, and the keys to a new Mercedes car, Nalbandian joked with Federer: "Roger, don't worry, it's not your last final.
"You're going to win a lot of tournaments, so let me keep this one."
Federer was typically magnanimous despite the painful manner of his defeat.
"I congratulate David for coming back from the two tie-breaks, which was tough," he told the crowd. "He got me and he totally deserved to win."
The Swiss also said he had no regrets about battling back early from injury in an attempt to defend his Cup crown.
Federer had a six-week lay-off because of an ankle problem prior to the season-ending event.
But he said: "I knew I was putting all those records on the line when I came here. It's just a pity I was so close.
"To be back after injury - I'm happy I made it so far. I'm proud of that."