NONTHABURI, Thailand (AP)—Rafael Nadal was knocked out of the Thailand Open on Saturday, losing 2-6, 7-6 (3), 6-3 to 53rd-ranked Guillermo Garcia-Lopez in an all-Spanish semifinal.

Fresh off his U.S. Open victory for a career Grand Slam, the sport’s No. 1 player was undone by Garcia-Lopez’s string of winners and flat, wide serves that included 10 aces.

“It’s a difficult loss to accept,” Nadal said. “It’s one of those matches you are going to lose once every two years.”

Added Garcia-Lopez: “Everything was fantastic. For the moment, I’m a bit shocked.”

On Sunday, Garcia-Lopez will play his second ATP final of the season. He will face 60th-ranked Jarkko Nieminen of Finland, who beat Benjamin Becker of Germany 6-3, 6-2.

Nadal was trying to win his seventh tournament of the year. Signs of trouble emerged in the second set when Garcia-Lopez started dictating important shots. At one stage, he whipped a groundstroke deep to the Spaniard’s backhand and forced him to throw his racket in an unsuccessful attempt to reach the ball.

“He played a great match, especially in the third,” Nadal said. “I had a great chance to be in the final. I have to blame myself that I didn’t play aggressive when I had a chance to break. He served well on break points. I lost chance after chance.”

Nadal was playing his first tournament since winning the U.S. Open and becoming the seventh man to complete a career Grand Slam. He is to play next at the Shanghai Masters, beginning Oct. 10.

Garcia-Lopez rode his momentum through the third set, applying pressure and forcing errors by Nadal, who converted only two of 26 break-point opportunities.

“I’ve never beaten a No. 1 player in the world,” Garcia-Lopez said. “I think this is the best victory in my career.”

Nieminen reached his first final of the year with sharp groundstrokes and an accurate first serve.

“I feel great,” Nieminen said. “I haven’t been in a final for a while, the last time was in Sydney 2009.”

The Finn has not dropped a set in his run to the final, including wins over No. 7-seeded Viktor Troicki in the second round and No. 3-seeded Jurgen Melzer in the quarterfinals.