Venus Williams ended her sister Serena's quest for a fourth straight WTA Key Biscayne crown on Tuesday as she triumphed in straight sets in the pair's first meeting since the 2003 Wimbledon final. Venus advanced to a semi-final showdown with reigning Wimbledon champ Maria Sharapova with a 6-1, 7-6 (10/8) victory. The elder Williams sister, 24, kept herself on track for a fourth Key Biscayne title to go with those she won in 1998, 1999 and 2001.
On the men's side, world number one Roger Federer kept his quest for a first Miami ATP Masters Series title alive, but the Swiss superstar was extended to three sets for the second night in a row.
Federer won his 19th straight match, a 6-3, 4-6, 6-4 victory over big-serving Croatian Mario Ancic.
Once again he showed his ability to find a way to win despite a sub-par day. But even Federer gets frustrated.
"As the match went on, he started to serve better. I only got a couple of chances, and I missed those," he said. "Threw my racquet a couple of times, which doesn't happen very often."
Federer lined up a quarter-final clash with sixth-seeded Briton Tim Henman, a 7-5, 6-3 winner over Czech Radek Stepanek.
Ninth-seeded American Andre Agassi, making his 19th appearance in a tournament he has won six times, defeated seventh-seeded Argentinian Gaston Gaudio, the French Open champion, 7-6 (9/7), 6-2.
Once he had put the first set away, on his fifth opportunity in the tiebreaker, Agassi made quick work of Gaudio.
Agassi will next face compatriot Taylor Dent, who beat Germany's Florian Mayer 6-3, 6-4.
Rising Spanish star Rafael Nadal, winner of two titles already this year, beat Croatian Davis Cup hero Ivan Ljubicic, the 13th seed 6-4, 6-7 (5/7), 6-3.
Nadal will face Sweden's Thomas Johansson, who beat Czech Jirk Novak 7-6 (7/2), 6-2.
Slovakia's Dominik Hrbaty, who ousted third-seeded Safin in the third round, reached the quarter-finals with a 6-3, 6-3 victory over French 18-year-old Gael Monfils, who received a wildcard into the tournament. Hrbaty will next face Spain's David Ferrer, a 6-7 (7/9), 6-3, 7-5 winner over compatriot Juan Carlos Ferrero.
The night, however, belonged to the Williams sisters, who lived up to their star billing with a tense, action-packed match in which Venus, for the first set, seemingly couldn't put a foot wrong.
"There was nothing I could do in the first set," said 23-year-old Serena, who had won the past six encounters with her sister to lead their career head-to-head 7-5 coming into the match.
In the second, a few more unforced errors crept into Venus's game, but Serena still couldn't gain the upper hand.
"I had plenty of chances in the second," said Serena, who had break chances in the second and fourth games before the two traded breaks in the fifth and sixth. "We should still be out there."
Venus, too, missed some opportunities in the second, failing to convert break points in the seventh and ninth games en route to the tiebreaker.
"The second set I felt like I lost some opportunities," Venus said. "I would have liked to have held serve when I got the first break in the second. But credit to Serena. It's not like she gave me that many points. Especially when she got down - big first serve, great approach shot. I had my hands full."
Her first match point came at 6-5 in the breaker, but she hit a backhand wide. Serena then had two set points, at 7-6 and 8-7.
But Serena handed Venus another match point when, with an open court to hit into, she dumped a forehand into the net. She followed that with a backhand long and then gave her sister a rueful hug at the net.
In the semi-finals, Venus will face Sharapova for just the second time. The Russian won their only previous meeting at last year's Zurich quarter-finals.
Sharapova, 17, posted a 6-1, 6-7 (6/8), 6-2 victory over Henin, who was playing in her first tournament of the year after battling illness and injury.
The Russian appeared to be cruising into the final four when she led the 22-year-old Belgian 6-1, 4-1. But when Sharapova served for the match at 5-4 in the second and led 40-0, Henin forced the game to deuce and broke for 5-5 when the Russian double-faulted on break point. At that point, Sharapova said, "You just keep fighting, keep being postive. It's all mental."
Henin squandered four set points in the 12th game before finally levelling the match in the tiebreaker.
But Sharapova raced to a 3-0 lead in the third and broke Henin in the final game to claim the win.
COLLATED RESULTS (x denotes seed): Men's (4th round): Dominik Hrbaty (SVK) bt Gael Monfils (FRA) 6-3, 6-3; David Ferrer (ESP) bt Juan Carlos Ferrero (ESP) 6-7 (7/9), 6-3, 7-5; Rafael Nadal (ESP) bt Ivan Ljubicic (CRO x13) 6-4, 6-7 (5/7), 6-3; Andre Agassi (USA x9) bt Gaston Gaudio (ARG x7) 7-6 (9/7), 6-2; Thomas Johansson (SWE) bt Jiri Novak (CZE) 7-6 (7/2), 6-2; Roger Federer (SUI x1) bt Mario Ancic (CRO) 6-3, 4-6, 6-4; Tim Henman (GBR x6) bt Radek Stepanek (CZE) 7-5, 6-3; Taylor Dent (USA) bt Florian Mayer (GER) 6-3, 6-4.
Women's (Quarter-finals): Maria Sharapova (RUS x2) bt Justine Henin-Hardenne (BEL) 6-1, 6-7 (6/8), 6-2; Venus Williams (USA x8) bt Serena Williams (USA x3) 6-1, 7-6 (10/8).