Serena wins sister showdown

KEY BISCAYNE, Fla. -- Serena Williams retained the No. 1 world ranking by being the best player in her family Thursday 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 keep 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."

If Venus had won, No. 2 Dinara Safina would have supplanted Serena in next week's rankings.

"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 today will be No. 4 Andy Murray, who beat No. 8 Fernando Verdasco, 6-1, 6-2.

Serena Williams will try for a 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 January's Australian Open.

Serena raced to a 4-1 lead over Venus 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.

"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 most heading back to the mainland by the third set.

The players were subdued, too, wearing impassive expressions and refraining from demonstrative reactions to points -- until the final game.