Andy Murray went out of the BNP Paribas Open with a three-set quarter-final defeat by Juan Martin del Potro in Indian Wells.
The Argentine faced just two break points and did not drop serve once as he won 6-7 (5-7) 6-3 6-1.
He faces Novak Djokovic in the last four after the top seed thrashed Jo-Wilfried Tsonga 6-3 6-1 in 53 minutes.
Rafael Nadal, who knocked out Roger Federer, will play Tomas Berdych in Saturday's other semi-final.
Murray was expected to join them as the number three seed, and went into the quarter-final with a 5-1 lead in past matches against Del Potro.
However, their last encounter came way back in 2009 and this time around the Briton found it hard to make an impression on Del Potro's heavy serve and huge forehand.
After Murray saved two break points in the opening game there were to be no more for either player in the next 50 minutes, and after winning an epic 43-stroke rally in the tie-break the Scot converted his second set point.
Del Potro's challenge might have been expected to fade, but quite the opposite - a break to love gave him renewed impetus at the start of the second set and he went close to breaking again as he levelled the match.
With the temperature in the Californian desert around 35C, both players looked to be feeling the effects in a tense decider.
Murray was especially edgy after he finally earned a first break point of the day, only to see Del Potro thump down a huge second serve.
The Briton then offered up a double-fault, a backhand error and a wayward forehand to help his opponent break, and when Del Potro doubled the advantage at 4-1 there was no way back for Murray.
A seventh double-fault gave Del Potro two match points and an eighth handed him victory after two hours and 32 minutes.
Murray will now head to Miami for the Masters event that begins next weekend, while Del Potro must recover in time to face world number one Djokovic on Saturday.