Del Potro knocks out erratic Murray

US Open champion Andy Murray made a slew of unforced errors as he was knocked out of the BNP Paribas Open quarterfinals by Argentina's Juan Martin Del Potro on Friday.

Though the British world number three edged a close first set 7-5 on the tiebreak, he lost serve once in the second and three times in the third to make a premature exit from the ATP Masters 1000 event.

Seventh-seeded Del Potro will next face world number one Novak Djokovic, who was barely tested as he demolished Jo-Wilfried Tsonga 6-3 6-1 earlier on Friday to extend his unbeaten run to 22 matches.

On a sweltering afternoon at Indian Wells, Murray saved two break points in the first game of the match but there were no further opportunities for either player as a closely contested opening set went into a tiebreak.

A big forehand winner by the Scotsman earned him a 5-2 lead but he double-faulted and then netted a forehand, screaming to himself in disgust, as he let Del Potro pull back to 5-4.

The Argentine then hit a backhand long for Murray to earn his first set point at 6-4 and, though he squandered that with a wayward backhand, he clinched the set at the next opportunity on a backhand error by his opponent.

However, the Scot failed to take advantage and was broken to love in the second game of the second set after double-faulting. Del Potro served out to level the match, clinching the set with a leaping overhead smash.

Murray was again broken in the third game of the final set, after netting a forehand, and also in the fifth, after hitting a backhand long, to trail 1-4.

Unable to break the towering Argentine's serve, Murray's challenge faded quickly and the match ended after two hours 31 minutes when the Scotsman double-faulted for an eighth time.

Top seed Djokovic delivered a ruthless display against the eighth-seeded Frenchman Tsonga in the first match of the day, breaking his error-prone opponent twice in each set and not dropping a single point on his own serve in the second set.  

Wozniacki in final

Former champion Caroline Wozniacki battled through a marathon encounter to upset fourth-seeded German Angelique Kerber 2-6, 6-4, 7-5 on Friday and reach her third BNP Paribas Open final in four years.

The eighth-seeded Dane held off a late fightback by Kerber to scrape through in a wildly fluctuating contest lasting two-and-a-half hours.

In a match littered with 14 service breaks, Wozniacki led 4-1 and then 5-3 in the third set but the German clawed her way back to 5-6 before being broken for a seventh and final time when she netted a forehand.

Wozniacki will next face 2006 champion Maria Sharapova, who overcome fellow Russian Maria Kirilenko 6-4, 6-3 in the second semifinal.