KEY BISCAYNE, Fla. (AP) " As Rafael Nadal trudged to his chair, 6-foot-6 Juan Martin del Potro stood near the net and unleashed a jubilant scream that only he heard because the fans were roaring too.
The 20-year-old Argentine delighted a partisan crowd by upsetting the top-ranked Nadal 6-4, 3-6, 7-6 (3) Thursday in the quarterfinals at the Sony Ericsson Open.
"Wonderful for the crowd," Nadal said. "Terrible for me."
Del Potro had lost all nine sets in their four previous matches, but he was buoyed by a home-court advantage, with many transplanted Argentines in the crowd singing "Del-Po" between points.
"They helped me a lot," del Potro said.
Also drawing cheers was 19-year-old Victoria Azarenka of Belarus, who earned a berth in the women's final by beating Svetlana Kuznetsova 6-3, 2-6, 7-5.
The No. 6-seeded del Potro's opponent Friday will be No. 4 Andy Murray, who beat No. 8 Fernando Verdasco 6-1, 6-2. Murray broke serve five times and saved seven of eight break points against him.
Del Potro showed patience in long rallies and used his looping forehand to keep Nadal deep as their three-hour match built to a dramatic finish.
"I beat him with my mind and with my game," del Potro said. "When we played long points, I was dominating every time."
Nadal was up two breaks in the final set at 3-love, but del Potro climbed back into the match by winning 12 of the next 14 points.
"I played really bad all the time," Nadal said. "When I have it 3-love in the third, I played worse. It was amazing disaster."
When Nadal lost serve for the second consecutive time for 3-all, del Potro let loose his primal scream. There was more noise to come.
In the 12th game of the set, Nadal saved three match points, two with aces. He caught a break in the tiebreaker when his return skipped along the net cord before clearing it for a winner and a 3-2 lead.
That was the last point Nadal won. Del Potro hit three consecutive winners to go up 6-3, and on the final point Nadal put a backhand in the net as the crowd erupted one last time.
"I beat the No. 1," del Potro said. "If you don't play unbelievable, you cannot beat him."
Nadal is a six-time Grand Slam champion, and he won at Indian Wells two weeks ago, but his best finish at Key Biscayne was as the runner-up in 2005 and 2008.
"I didn't play well during this tournament," Nadal said. "I didn't adapt well. I played really bad."
Azarenka kept waving clenched fists during her semifinal, as if there was any doubt she meant business. Celebrating every important point she won, the teenager earned her biggest victory yet.
She'll play for the title Saturday against the winner of the semifinal Thursday night between Serena and Venus Williams.
"It's the first final in such a big tournament for me," the No. 11-seeded Azarenka said. "It's the biggest moment, I would say, in my career. It's all kind of an experience for me. It's a new thing that I'm going to be introduced to on how to handle."
Azarenka closed out the victory on her fourth match point when Kuznetsova netted a backhand to end the 2-hour, 40-minute endurance test played in 85-degree sunshine.
"I'm just so happy that I found energy in that fighting moment," Azarenka said. "That was kind of adrenaline, I would say, on the last games."
Azarenka, who trains in Scottsdale, Ariz., is ranked a career-best 10th after reaching the semifinals at Indian Wells two weeks ago.