Czech Tomas Berdych halted fifth seed Juan Martin Del Potro's hot streak by beating the Argentine 6-1, 6-4 to win the Japan Open on Sunday.
Ninth seed Berdych's fourth ATP Tour title and his first since winning on grass in Halle last year came after Del Potro left the court to take medicine for an upset stomach.
"Everyone could see he had some problem," said Berdych, who stunned second seed Andy Roddick in the semi-finals. "But he took some pills and was getting back into the match.
"It might have been different if Juan Martin was feeling better but I served well and everything came together."
Del Potro had been strong favourite to win the final at the $969,000 Tokyo hardcourt tournament having won 29 of his previous 30 matches but Berdych dominated from the start.
Warned for taking too long for a lavatory break after the fifth game, Del Potro took a medical timeout for stomach problems after surrendering the first set in just 22 minutes.
The 20-year-old Argentine, who recently helped his country reach the Davis Cup final, was broken again early in the second when Berdych forced him into a loose backhand.
Berdych's nerve held and he closed out a surprisingly comfortable victory with a huge serve Del Potro was unable to control.
The Czech picked up $135,000 for the win while Del Potro, conqueror of top seed David Ferrer in the last eight, boosted his hopes of a place at the season-ending Masters Cup.
Del Potro will climb to ninth in the race for next month's lucrative eight-man Shanghai shootout and a career-high ninth in the ATP world rankings.
"His game confused me," admitted Del Potro, whose only loss in his previous 30 outings had come against Briton Andy Murray in the US Open quarter-finals.
"I took some medicine and I started playing a little bit better but it was too late. I didn't have any chance today. He played great. It was his day."
Rafael Nadal, Roger Federer, Novak Djokovic and Murray have already qualified for the eight-man Shanghai shootout.
In the women's event, top seed Caroline Wozniacki won the lower-tier tournament, beating fifth-seeded Estonian Kaia Kanepi 6-2, 3-6, 6-1 to take the top prize of $28,000.
It was the 18-year-old Dane's third WTA Tour title following wins in Stockholm and New Haven earlier this year.