Marcel Granollers knocked fellow Spaniard and former champion David Ferrer out of the Japan Open in a first-round upset on Monday 4-6, 6-4, 6-4.
The win over the tournament's second seed was the first for Granollers in six meetings with his compatriot, ranked fifth in the world.
The early loss is a blow to Ferrer's chances as he fights to qualify for one of five remaining spots at the season-ending ATP World Tour Finals in November in London.
Ferrer, who also went out in the first round in Shenzhen last week, went down in just over two hours after his serve was broken four times.
"Every day in life is different," said the disappointed Spaniard. "It's impossible to win all the time."
"In the second set I lost my focus and in the third he played better and took advantage. I'm sad to lose, I need to see what is going on with my game."
Granollers rallied after losing the opening set, taking a 5-1 lead in the second set before Ferrer, known as a dogged competitor, pulled it back to 4-5.
But Granollers went on to take the set in the next game, bringing about a deciding set.
The pair traded breaks from the fifth through seventh games as Ferrer dropped serve for the second time, 3-4.
The 2007 champion stayed in touch at 4-5 but was defeated a game later after saving two match points. Granollers converted on his third with a cross-court volley that left Ferrer with no chance.
South African seventh seed Kevin Anderson held off rising young ATP player Dominic Thiem 7-6 (7/5), 6-4 to advance to the second round.
Thiem, who at 21 is the youngest player at the Ariake Colosseum in Tokyo, reached the forth round of the US Open a few weeks after playing a final at home in Kitzbuehel.
Anderson took just one hour and 45 minutes, with 11 aces and four breaks of serve to claim his victory.
"He's a good player with a lot of potential," said Anderson. "I was pleased to get through. It's been a couple of weeks since I played in New York (at the US Open).
"Sometimes after all that time between matches it can be tough. I'm happy with how I was able to play.
"Conditions were tricky as centre court was actually a bit slow. The balls got heavy after a while.
"But I was moving well and serving well. I played good tennis. I was relaxed on my service games, which is important."
The tournament field on the second week of a three-week Asian ATP swing is headed by Australian Open winner Stan Wawrinka, with Canadian Milos Raonic, the losing finalist at the last two editions (to Kei Nishikori and Juan Martin del Potro), taking the third seeding.
US Open finalist Nishikori arrived home on Monday after winning his third season title in Kuala Lumpur at the weekend with the defeat of French player Julien Benneteau.
Elsewhere in the first round, American Steve Johnson defeated Japanese qualifier Hiroki Moriya 7-6 (7/4), 6-2. Gilles Muller beat Argentine Federico Delbonis 6-3, 6-4 and Kazakh Andrey Golubev put out Pierre-Hugues Herbert of France 6-4, 6-4.
Source: AFP