The Associated Press

KEY BISCAYNE, Fla. - Sidelined by knee surgery, Serena Williams spent most of the past eight months designing dresses and dabbling in acting.

Now that she's ready to get back on a tennis court, it's as if she never left: Williams will be seeded No. 1 at the Nasdaq-100 Open, which begins today.

"I really, really am excited about getting back," said Williams, the two-time defending champion at Key Biscayne. "I've been in a lot of pain watching a lot of players play when I really want to be out there."

The tournament will be her first since she won her sixth Grand Slam title by beating older sister Venus at Wimbledon in July.

Despite the long layoff, Williams returns as the favorite - thanks to a series of withdrawals. The four top-ranked women are missing, including Justine Henin-Hardenne and Kim Clijsters.

Williams is hardly the only star who has been hurt - or even the only Williams. Venus missed the final six months of the 2003 season because of an abdominal injury, and a sore right knee has limited her to six matches this year.

"It's been really tough for her to get back," Serena said. "We've both been working very hard, and we both plan on making a lot of noise."

With the sisters seeded 1-2 this week, they can meet only in the final. Serena has beaten Venus six times in a row.

The 32 seeded players receive first-round byes, meaning they'll play their opening matches Friday or Saturday.

No. 1-ranked Henin-Hardenne decided to skip Key Biscayne, even though it is regarded by many as the most prestigious tournament outside the majors.

Also missing will be No. 2 Clijsters, who tore a tendon in her left wrist. No. 3 Amelie Mauresmo is out due to a back injury, and No. 4 Lindsay Davenport decided to join Henin-Hardenne and take a break.

Men's favorites include Top-ranked Roger Federer and No. 4-seeded Andre Agassi, who is bidding for his seventh Key Biscayne title and fourth in a row. He and No. 2 Andy Roddick are in the tougher half of the draw.

The only top 20 men's player absent is French Open champion Juan Carlos Ferrero, who is sidelined by chicken pox.