Juan Martin del Potro claimed a second straight Swiss Indoors trophy on Sunday with a 7-6 (7/3), 2-6, 6-4 win over Roger Federer to earn his second title in a month.
Even though Federer lost a chance to clinch a spot in the ATP World Tour Finals in London from November 4, the Swiss can assure himself a place in the eight-man field by winning his opening second-round match next week at the Paris Masters.
Federer will face the winner from Russia's Mikhail Youzhny, the Valencia champion on Sunday, and South African Kevin Anderson.
He if wins he will be into the London year-ender for a 12th straight edition where he would be bidding for a sixth title.
Del Potro, the Tokyo champion three weeks ago, profited after Federer, who had squared the match at a set each, double-faulted twice in the opening game of the final set in front his 9,200-strong home public at the event which he has won five times from ten finals.
"I played my best match of the week today," said the Argentine winner who could not stop expressing his respect for Federer, the 17-time Grand Slam champion.
"Roger is a great person and he has already won this title too many times.
"I know how it feels to lose big matches like this. I played well today and felt I got better at the end. My last two service games were the best I could have hoped for."
Del Potro has now defeated Federer in their last three matches.
"It's always a pleasure to play Roger. He's the hero here and for me my biggest inspiration. You make history at every tournament you play."
Federer fired 14 aces to no avail in the final as he failed to win what would have been just a second title in a disappointing season.
"I may have lost but it was perhaps my best match of the week," said Federer. "It was a high level. But it's hard to judge when you lose.
"I shouldn't have handed the break over to him so easily in the third set (first game) but overall I did well today.
"I felt I was getting better in the third set but at the end he wasn't giving me anything. Overall it was a great week. I'm happy to have some tough matches and withstood the challenge.
"Physically I'm fine. The crowd gave me amazing support, which makes it easier when you lose a match like this."