Juan Martin del Potro saved three championship points as he stunned world number one and defending champion Roger Federer 6-4 6-7 (8-10) 7-6 (7-2) in an absorbing Indian Wells Masters final.
Del Potro was down 5-4 and a match point in the final set against 20-time grand slam champion Federer, who was on the cusp of a record sixth title at Indian Wells.
However, big-hitting Del Potro – who beat Federer in the 2009 US Open final – emerged from the jaws of defeat to snap the Swiss' 17-match winning streak to open the season.
The thrilling victory – lasting almost three hours – secured a maiden Masters 1000 title for world number eight Del Potro and just his seventh win in 25 attempts against Federer.
Federer was chasing his 28th Masters 1000 crown and 98th ATP title overall but he was upstaged by Del Potro early, the Argentine star losing just six points on serve in the opening set.
Del Potro struck the first blow, a second loose Federer forehand of the fifth game crashing into the net to leave the favourite a break down at 3-2.
The steely Argentine did not allow Federer a look-in in the first set, maintaining his advantage courtesy of such a potent forehand and powerful serve.
Federer did not have a single break point opportunity in a first set which Del Potro won when his opponent sent a forehand wide.
The crowd were off their seats when Federer produced a brilliant winner at full stretch in the first game of the second set and rose again when he won an epic rally which Del Potro kept alive with a between-the-legs shot from the baseline.
Federer made another uncharacteristic error by slapping a simple forehand in the net to make it 3-3 and he was left frustrated when a defiant Del Potro saved two set points at 5-4.
Del Potro managed to force a tie-break but he was no match for Federer, who outlasted his powerful opponent to finally force a decider.
There was more drama in the final set as Del Potro prevented Federer from claiming the title at 5-4, his brute power unnerving the 36-year-old, whose frustration was apparent.
And Federer cut a forlorn figure in the eventual tie-break, which Del Potro won at a canter to become the first player from Argentina to reign supreme at Indian Wells.