Basel - Juan Martin del Potro took Roger Federer's Swiss Indoors title on Sunday, beating the hometown favourite 6-4, 6-7 (5/7), 7-6 (7/3) in the final.
Del Potro showed an impressive all-around game to help avenge a heartbreaking loss to Federer in the Olympics Games semi-finals in August.
"It's amazing for me," Del Potro, who never dropped serve, said in an on-court interview. "Always, playing against Roger is a pleasure. We know he's the best player ever in this sport."
Federer, who won the event in five of the past six years, was seeking his 77th career title to tie John McEnroe at fourth on the Open Era list.
Del Potro ended a six-match losing streak against the top-ranked Swiss this year, which also included a five-set defeat at the French Open.
"You deserved it," Federer told his opponent on court. "You had a couple of tough losses against me this year and I'm really happy for you."
The 24-year-old Argentinian won for the second straight week, after taking the Vienna title. His fourth title of the season is the 13th of his career.
Del Potro's victory in 2 hours, 44 minutes compared to his 4-hour, 26-minute defeat at the Olympics -the longest three-set match in history - when Federer won the decider 19-17 on Centre Court at Wimbledon.
As he did at Roland Garros and the Olympics, Del Potro took the first set, breaking Federer's serve in the fifth game.
Federer struggled briefly with his groundstrokes, netting two forehands and a backhand to give Del Potro the lead.
The second-seeded Del Potro relied on solid serving and unleashed blistering forehands when needed. He took his first set point chance when Federer sent a backhand wide.
Both players wasted their only break chances in the second set, which hinged on a tense Federer service game at 5-5.
Facing break point, Federer struck a forehand crosscourt winner then saw Del Potro slip up by netting a sliced backhand on the next point.
Federer controlled the tie-breaker and punched the air when he levelled the match, as Del Potro let a backhand drift wide.
Federer held three break points at 1-1 in the deciding set, but Del Potro saved them before firing an ace to win the game.
A wild Federer forehand let another break chance slip in the seventh game, which Del Potro clinched with another ace.
Federer then struck three straight aces when threatened at 5-6 down to force another tie-breaker.
Del Potro seized his chance after Federer netted a topspin forehand, and clinched on his first match-point chance on another wayward forehand from the top-seeded Swiss.