Serena Williams retained the No. 1 world ranking by being the best player in her family last night.
Williams defeated older sister Venus 6-4, 3-6, 6-3 in the semifinals of the Sony Ericsson Open. It was their 20th sibling showdown, and each has won 10 times.
Serena needed to reach the final to retain the top ranking she has held since Feb. 2.
"I'm excited," Serena said. "I was thinking I'd love to remain No. 1. I think I was more happy about that than winning the match."
"Even though she's my sister, I'm still here to win," Venus said. "I can't give anyone anything. So I'm disappointed that I lost tonight, whether or not she kept the ranking."
No. 1 Rafael Nadal lost in the men's quarterfinals to 20-year-old Argentine Juan Martin del Potro, 6-4, 3-6, 7-6 (3). The upset delighted a partisan crowd that included many transplants from Argentina.
"Wonderful for the crowd," Nadal said. "Terrible for me."
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.
Serena Williams will try for a record sixth Key Biscayne title Saturday against 19-year-old Victoria Azarenka of Belarus, who beat Svetlana Kuznetsova 6-3, 2-6, 7-5. Azarenka became sick to her stomach before losing a fourth-round match against Williams at the Australian Open in January.
Serena raced to a 4-1 lead in the final set and broke serve for
the sixth time in the last game. When she closed out her victory, she hopped in delight, raised a fist and shouted "Yes!" She then met her sister at the net with a handshake and slap on the back.
"It never gets easy," Serena said. "She's the toughest player I think on the tour, besides me of course."
As often happens, Williams vs. Williams was an aesthetic disappointment. Both players repeatedly went for winners, which resulted in many errors and few long rallies. Fans were subdued, with the majority heading back to the mainland by the third set.
The players were subdued, too, wearing impassive expressions and refraining from any demonstrative reactions to points -- until the final game.
With Venus serving at 3-5, Serena hit a backhand winner and punched the air, then repeated the sequence five points later to reach match point.
"It was a well-fought match," Venus said. "My serve wasn't going as well as I wanted. But she brought a lot of balls back and played tough."
Del Potro had lost all nine sets in his four previous matches against Nadal, but the Argentine was buoyed by a home-court advantage, with many fans singing "Del-Po" between points.
"They helped me a lot," del Potro said.
The 6-foot-6 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 a primal scream.
"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.
"It's the first final in such a big tournament for me," the No. 11-seeded Azarenka said. "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."