Andy Murray was beaten 6-3 7-5 by world number three Roger Federer in the quarter-finals of the Western & Southern Open in Cincinnati.
After losing the first set, Murray, 27, fought back to lead 4-1 in the second, but lost six of the final seven games.
Federer, 33, now faces Canadian Milos Raonic in a re-match of their semi-final meeting at Wimbledon in July.
"I don't remember hitting very many good shots after the 4-1 game. I blew it, it's a shame," said Murray.
Federer dominated from the start and forced Murray to save six break points before making the decisive break in the fifth game.
A series of Murray forehand winners gave him a double-break 4-1 lead in the second set, but he lost three of his next four service games as Federer rediscovered his first-set form.
Murray has not won an ATP ranking event or beaten a top-10 player since Wimbledon in 2013 and since having surgery on a back injury last September his ATP world ranking has slipped from third to ninth.
|Andy Murray's story of 2014|
|Qatar Open||second round|
|ABN Amro World Tennis Tournament||quarter-finals|
|BNP Paribas Open||fourth round|
|Madrid Masters||third round|
|Queen's Championships||third round|
|Western & Southern Open||quarter-finals|
World number 41 Julien Benneteau upset Australian Open champion Stan Wawrinka 1-6 6-1 6-2 to reach the semi-finals and now plays David Ferrer, who defeated Tommy Robredo 6-4 3-6 6-3.
In the women's draw, world number one Serena Williams is on track for a first Cincinnati title with victory over Jelena Jankovic in the last eight.
The American won 6-1 6-3 to set up a semi-final against Caroline Wozniacki, who beat fourth seed Agnieszka Radwanska 6-4 7-6 (7-5).
Maria Sharapova fought back to beat second seed Simona Halep 3-6 6-4 6-4 in a clash of the two women with the most wins in 2014, and a repeat of the French Open final won by the Russian.
"Nothing really was going my way," said Sharapova. "So I definitely needed to do a few things differently to be a bit more consistent but maintain that aggressiveness that works against her.
"The court is like a battlefield. It's my job. It's where I'm supposed to perform."
Sharapova will play ninth seed Ana Ivanovic in the semi-final, after the world number 11 beat Elina Svitolina 6-2 6-3.