Juan Martin del Potro shocked world number one Rafael Nadal in the quarterfinals of the Miami ATP Masters 1000 Thursday, downing the top-seeded Spaniard 6-4,3-6,7-6 (7/3).

In the semifinals, the sixth-seeded Argentinian will face world number four Andy Murray of Britain, who beat eighth-seeded Spaniard Fernando Verdasco 6-1,6-2.

Nadal, who won his sixth Grand Slam title at the Australian Open, also won the first Masters 1000 crown of the year at Indian Wells in March.

He had won all four of his previous meetings with del Potro without dropping a set - including a quarterfinal victory at Indian Wells.

But before a raucous, largely pro-del Potro crowd the Argentinian fought back from 0-3 down in the third set to prevail in the tiebreaker.

"Today, I did everything," del Potro said. "I served very good, and hit with my forehand with big confidence.

"To beat Rafa, you have to be in good shape in every part of your game, and today I did a greatjob."

Nadal saved three match points in the 12th game of the final set - two of litem with aces - to force the tiebreaker.

But del Potro was not to be denied, winning the final five points of the decider to advance.

Del Potro hit three straight winners to give himself three more match points at 6-3 in the tiebreaker. Nadal fired a backhand into the net on the first of them, sending the fans into a frenzy.

"Wonderful for the crowd, terrible for me," said Nadal, although he said he enjoyed the excitement surrounding the three-hour duel.

"That's good for tennis, to have a crowd like this. It was a really good atmosphere."

Nadal, who also reached the final in Rotterdam in February as his 2009 campaign got off to a sizzling start, said he didn't play well, but he praised his rival. "I have no excuses. Juan Martin played better than I did," Nadal said.

Even so, Nadal said the whole match was a struggle for him.

"I think I played really bad all the time," Nadal said. "When I have 3-0 in the third 1 played worse. It was amazing disaster."

Nadal said he never felt at home in Miami, even though he arrived fresh from his California triumph

"I didn't adapt well to this tournament this time," he said, adding that he would take a few days off then start his preparations for the claycourt season.

The defeat means Nadal leaves Miami empty-handed again. He has never lifted the trophy here, with runner-up finishes in 2005 and last year his best showings.

Murray, who has been closing in on the world number three spot now occupied by Novak Djokovic, made quick work of Verdasco, who was injured early in the match.

Murray broke the Spaniard five times and saved seven of eight break points he faced.

"I saw him get a bit frustrated early in the match," said Murray, who is dosing in on the world number three ranking of Novak Djokovic. "I stayed on top of him throughout. Didn't give him too many chances.

"There was a big game early in the second set when I was down love-40 on my serve. Once I won that, 1 felt very comfortable," die Scot added.

Murray said he wouldn't be counting on del Potro having a let-down after beating Nadal, but he said the fact that the Argentinian's match was such a bruising affair had to be in his own favour.

"I'm sure he's in good physical shape,” Murray said. "But it was a pretty brutal match today and a lot of long points. Both guys did a lot of running. You know, obviously better for me the longer the match went.

"Mine was a quick one, so in that respect that's obviously an advantage to me. But, you know, he's obviously still going to be very dangerous."