After eight months out of the game, the woman who once dominated tennis has finally been making her comeback.
Serena has not played since winning Wimbledon last July
But there are those who think that her time at the top is over.
Back in July last year, it was all so different. Serena's win over her sister Venus at Wimbledon was her fifth Grand Slam title out of the last six.
She had held the number one ranking for 57 consecutive weeks and was about to sign a £34m sponsorship deal with Nike that would make her the highest-paid sportswoman in the world.
When she went under the surgeon's knife at the start of August, the prognosis was that she would be out for just eight weeks - enough to force her to miss the US Open, but not enough to seriously loosen her iron grip on the women's game.
But as the weeks slipped by, and the partially-torn tendon in her left knee refused to heal, the doubts began to grow. The first deadline for her comeback came and went with no sign of Serena anywhere near a tennis court.
In September she suffered the trauma of losing her half-sister Yetunde Price, who was shot dead in Los Angeles just a mile from the public courts where the Williams sisters had first learned to play.
Serena pinpointed a return at the Hopman Cup in January, only to announce that she would be back instead to defend her title at the Australian Open.
That didn't happen. Neither did the Paris Open, nor the Qatar Open.
In the meantime, lots of other - non-tennis - projects did. Serena was seen everywhere except on court - starting the Ford 400 motor race, down the front at the NBA All-Star Game and at the MTV Awards.
Her acting career certainly got a boost, with roles as a kindergarten teacher on ABC's 'My Wife's Clothes', a reformed gang member on Showtime's 'Street Time' and as a beach volleyball player in a Nike advert.
There was time for a photoshoot for Sports Illustrated's swimsuit issue, an appearance in an LA fashion show and a slot doing the voice on a film called SpongeBob Square Pants.
Meanwhile, Justine Henin-Hardenne was making hay while she could. With Venus also struggling with injury, the toned-up Belgian began to clean up.
Serena's interest in fashion has grown during her time out
And even though Serena is now fit and, she says, focused on her tennis, not everyone shares her opinion that she can take that number one ranking back off Henin-Hardenne.
''I'm very confident I can still win, and if I didn't feel that way, I wouldn't bother coming back,'' says Serena.
"I've been hungry to come back for quite some time, and I'm ready."
Henin-Hardenne is not so sure.
"I don't think you can come off all that time not playing and come back and win everything," she says.
"It's going to be difficult for her. I think that neither of them (Serena and Venus) will ever play 15 tournaments a year again, but to play 18 is not a lot for me. I am 21 years old and able to improve for many years to come."
Jelena Dokic is even more certain.
"That story is over,'' she says. "I don't even hear comments about Serena anymore."
Lindsay Davenport, who has herself spent time on the sidelines with injury problems, has warned Serena not to expect instant dividends.
''It will probably take her three to four tournaments or three to four months to really get back into the groove of playing matches and being back on the tour,'' she says.
Andre Agassi knows a bit about comebacks, having fallen outside the world's top 100 in 1997 only to climb back to the number one slot and win Grand Slam titles at an age when most players are considered finished.
"I don't think it's easy, but if anybody can make it look that way, I got a hunch she will," he says.
"She'll find more challenges than she's had before, but she's established herself as a great enough athlete to allow for a little margin there.
"When she gets on the court, it won't be as easy for her as it used to be, but she'll make up for it pretty quickly."