World number nine Gaston Gaudio came from behind to qualify for the Masters Cup semi-finals with a dramatic three-set victory over hard-hitting Chilean alternate Fernando Gonzalez.
The Argentine saved three match points before recovering to take the second set, and broke late in the third as Gonzalez smashed long and double-faulted to win 1-6, 7-5, 7-5 on Friday.
Gaudio's win ends a dream run for the 13th-ranked Gonzalez, who was partying at home just a few days ago before being called up as a reserve player. He was the first Chilean in a year-ending tournament since Marcelo Rios in 1998.
Gaudio, 26, will play world number one Roger Federer in the semi-finals, where he joins compatriot David Nalbandian. No Argentine had qualified for the last four of a season-ending tournament since 1983.
Pummelling the former French Open champion with groundstrokes of 122 kilometres per hour (76 miles per hour), the confident Gonzalez broke three times in a quickfire first set which lasted just 24 minutes.
Gaudio, screaming in frustration, let slip three break points in the fifth game of the second set and was broken for 3-5 as Gonzalez found a cross-court winner.
But the Argentine, who smashed his racquet in frustration while losing to Davydenko, calmed himself and saved three match points before breaking and serving out for the set.
As Gonzalez began to tire, Gaudio grew in confidence and broke in the third game of the decider with the Chilean firing wide. But with victory in his sights, he was broken back for 4-4 and then wasted three break points.
However, a charitable Gonzalez gifted a break point with a wild smash which missed an empty court by several metres, before putting Gaudio 6-5 up with a double fault.
The Chilean, who beat Mariano Puerta after replacing the injured Andre Agassi, put a forehand long on Gaudio's first match point after two hours and nine minutes.
Later, Nikolay Davydenko completed a flawless Masters Cup round-robin campaign with a 6-3, 6-2 victory over Mariano Puerta, handing the Argentine alternate his third straight defeat.
Davydenko, already in the semi-finals after straight-sets wins over Andre Agassi and Gaston Gaudio, broke at 4-2 in the second set before Puerta handed over the dead rubber with an overhit forehand after an hour and four minutes.
Puerta, a late replacement for the injured Rafael Nadal, was out of the reckoning after defeats by Gaudio and Fernando Gonzalez.
The defeat ends a difficult year for Puerta, who was forced to deny career-threatening newspaper claims in October that he had failed his second drugs test.
The 27-year-old left-hander served a nine-month doping ban in 2003.
It was also revenge for the Russian world number seven after he was beaten in five sets by Puerta in this year's French Open semi-final.