It is a bizarre quirk of the women's game right now that the world No 1 is routinely overlooked when it comes to considering who might win the US Open title.

Wherever she is ranked, whatever she has done in recent months, Serena Williams is the favourite and when she plays her best, she has proved she is virtually unbeatable.

But if the world No 4 is not quite on her game, or if she is having meltdowns as she did here in 2010 and 2011, then there are plenty of others good enough to take advantage.

The current forgotten woman is Victoria Azarenka, who, despite the fact she sits deservedly atop the rankings, having won her first Grand Slam title at the Australian Open in January, remains the archetypal puzzle wrapped inside an enigma.

The Belarussian lost top spot to world No 3 Maria Sharapova after the Russian won the French Open, but regained it after Wimbledon, when Serena beat Sharapova to win the title for the fifth time. Azarenka's consistency has kept her at the top and she has done little wrong of late, reaching the semi-finals at both Wimbledon and the Olympics, losing to Serena on both occasions.

As world No 1, people should be talking her up as a likely US Open champion, but almost every player who fulfilled their media obligations here yesterday was asked more about Serena than themselves.

Luckily for Azarenka, she does not care about such things and after a scare in Montreal this month, when she pulled out in her first match with a knee injury, she pronounced herself fully fit.

"I am feeling good," she said. "It was impossible for me to play in Montreal because it was just too soon after the Olympics. I was absolutely drained, physically and emotionally. But I was glad I could have a little time off to prepare for the US Open as best I can. I am feeling good now."

Having been beaten by Serena at Wimbledon and the Olympics, it would be understandable if the 23-year-old allowed herself a smile when she was placed in the opposite half of the draw to the American here.

Though the top half is loaded, with Sharapova, No 5 Petra Kvitova, China's Li Na and defending champion Sam Stosur, avoiding a potential clash with Serena would have been uppermost in her mind.

But the world's top woman player is only focused on herself and not on what happens with anyone else, including Serena.

"When I go into a tournament, I try to think of just my opponent on that particular day," she said. "The tournament is so long and you can't play perfect tennis all the way through; sometimes you have to struggle and win ugly. I just try to make sure I do my best if I can."

If Azarenka was happy to internalise her true feelings, Stosur was far less worried about keeping up appearances, admitting that the American was the one to beat.

"Serena is probably the favourite coming in, given her recent form," the Australian said. "I don't think you can really deny that."

Stosur beat Williams in an eventful final here last year, producing the performance of her life in the cauldron of Arthur Ashe Stadium to win her first Grand Slam title.

Having suffered under the pressure of home expectation at the Australian Open, she is far happier out of the spotlight, with no-one talking her up.

"It's fine whether you're talked of being the favourite or not," she said. "At this point in time I don't think it really matters. Everyone is starting from scratch, and things become clearer as the weeks go on."

Last year's win over Serena was a stunning effort, performed in the face of another meltdown from the American over an umpiring decision. Since then, Stosur has reached the semi-finals at the French Open, but other than that, has been largely disappointing. Returning to the scene of her greatest triumph, she hopes, will ensure a return to her best form.

"Hopefully it's a matter of time before it really starts happening again," she said. "I'm playing well. You just have to put it together at the right time."

Three-time champion Kim Clijsters, who has not lost here since 2004 and who is set to retire after the tournament, is a threat if she can stay fit throughout the fortnight while the likes of Sharapova, Li Na, Kvitova and world No 2 Agnieszka Radwanska will all fancy their chances.

Someone, however, will have to take out Serena if there is to be an upset. Azarenka believes she can do it, but Venus Williams, who continues to battle an incurable autoimmune disease called Sjogren's syndrome, gave the rest a warning about her sister. She said: "When she is fit and in form, it takes a hurricane to beat her."