Victoria Azarenka (left), Andy Murray (centre) and Serena Williams are seen laughing on the court during the Arthur Ashe Kids Day in New York. (EPA)

AFP/New York

Serena Williams is taking nothing for granted as she vies for a third straight US Open title, which would put her alongside two greats of the game.

The 32-year-old once known for stepping up her game when it mattered most has thrice been thwarted in 2014 in her bid to join Chris Evert and Martina Navratilova as 18-time Grand Slam singles champions. Although she has lifted five WTA trophies this year, she has failed to make it past the fourth round at the Australian Open, French Open or Wimbledon.

So she sounded wary of the suggestion that a return to Flushing Meadows, where she has won five US Open titles, would produce major number 18. “Yeah, Australian, Wimbledon, and French also could have been 18,” she said. “Didn’t quite happen.”

But Williams was firing on all cylinders as she won two hardcourt titles in the buildup to the Open, signalling she won’t surrender her crown without a fight. Her straight-sets win over Ana Ivanovic in the final at Cincinnati showed Williams at her dominant best.

“At some point of the match, I actually felt quite embarrassed walking from one side to the other for returns,” Ivanovic said of the near-hopelessness of returning Williams’ best serve.

It was a long way from Ivanovic’s fourth-round victory over Williams at the Australian Open, where the American was hindered by back pain. Back trouble, a humbling second-round exit at Roland Garros, and the virus that left her weak and woozy in doubles after her shock third-round singles exit at Wimbledon, are all in the past, Williams said.

“I’m in some of the best shape I’ve been in,” said the world number one. “I can play long points and be ready to go again. I feel really fit -- 32 is the new 22, right?”

An actual 22-year-old, Simona Halep, will be among those trying to topple Williams in New York. The Romanian has been knocking at the door of a first Grand Slam title this year, finishing runner-up to Maria Sharapova at Roland Garros.

Halep also reached the quarter-finals of the Australian Open and the semi-finals at Wimbledon as she climbed to number two in the world. Williams will also be challenged by more familiar foes, including Sharapova.

Sharapova’s appetite is only greater after she missed last year’s US Open with a shoulder injury that brought her season to a premature close. She sealed yet another return from injury by capturing her fifth career Grand Slam in Paris, but she has never won two majors in the same year. “I only have one more chance to do that this year,” she said, and admitted that such milestones matter. At this position, that’s where you showcase how strong you are and how much you really love it and (want) to show your legacy through the sport,” she said.

Just who else might emerge to challenge Williams is unclear. Australian Open champion Li Na of China is an injury absentee, while Czech Petra Kvitova was an early casualty in Canada and Cincinnati although she did claim the New Haven title on Saturday.

Eugenie Bouchard, who reached the semi-finals at the Australian and French Opens before becoming the first Canadian woman to reach a Grand Slam final at Wimbledon, has failed to impress since her crushing loss to Kvitova at the All England Club.

Azarenka injury cloud

Victoria Azarenka, beaten by Williams in each of the past two US Open finals, goes into the fortnight under an injury cloud. The Belarusian, owner of two Australian Open titles, has been limited to just six events in 2014.

She battled a foot injury for much of the year and withdrew from her title defence at Cincinnati with a right knee injury. The two-time Australian Open winner, is seeded 16th, but says the drop in her ranking doesn’t concern her and won’t change her approach.  “I never cared about that stuff,” she said. “I’m the same way if I was better ranked. I always know that it doesn’t matter how high you’re ranked or how well you play the tournament before. You’ve still got to start from zero.”

Russian veteran Svetlana Kuznetsova, who won the US Open in 2004, arrives in New York having snapped a four-year WTA title drought at Washington in August.

Australian Samantha Stosur—whose 2011 US Open triumph makes her the last woman to beat Williams in a final at Flushing Meadows—has had a largely forgettable season.

Also among the former champions in the field, Venus Williams has failed to shine in Grand Slams this year, but won her 45th career title at Dubai and reached the final at the US Open tune-up in Montreal—where she fell to Poland’s Agnieszka Radwanska. That Canadian run included a her first victory over younger sister Serena since 2009.