Caroline Wozniacki is getting sick of being asked the same question. After nearly every tournament, win or lose, it’s always the same, and it was once again the case after the WTA Championships in Istanbul last week after she bowed out in the group stage.

It’s a monkey on her back that doesn’t apparently bother her much, but it means the world to her critics: how can she truly be the top-ranked women’s tennis player without ever winning a grand slam tournament?

Going into the championships, which is the final significant tournament of 2011 and contested by the top eight in the WTA rankings, Wozniacki knew what she needed to do to ensure she would finish the year as world number one. And in the end, despite defeats to Vera Zvonareva and Petra Kvitova, a solitary win against Agnieszka Radwanska and Maria Sharapova’s failure to make the final made it mission accomplished.

“I think people do realise the true importance of [being number one],” she told British newspaper The Daily Mail. “If you ask any little boy or girl, everyone knows what it is to be number one. They might not know a grand slam … but if you are number one everyone knows you have done something remarkable.”

Starting and finishing the season at number one without winning a grand slam in between is a feat that has only been achieved once in the history of tennis – by Jelena Jankovic in 2008. And Wozniacki is one of just four number ones (men or women) to have failed to win a grand slam (Marcelo Rios, Dinara Safina and Jankovic are the others). And it’s not as if she keeps on losing in the finals – so far the 2009 US Open has been her only appearance. Yet somehow, Wozniacki remains positive.

“When you begin the season, everyone starts from zero and it’s the dream to be number one,” she told the Mail. “I’m so happy that I’ve been playing the most consistent and best tennis all year.”

But while Wozniacki is the most consistent, does that necessarily make her the best? She has spent more weeks at number one than Kim Clijsters, Maria Sharapova and Venus Williams combined, but she has nothing to show for it, while they have won 14 grand slams between them. 

Her critics claim Wozniacki plays too many tournaments in pursuit of the number one ranking. This year, only Marion Bartoli has played more matches (82 to Woz’s 80), and nobody comes close to matching her 58 victories. And there were worrying signs of fatigue in her final match in the WTA Championships – her third in three days – which led to her getting her blood pressure checked after the first set.

And it is also claimed that she relies too much on defence. At the WTA Championships once again, this was evident in the stats. She only managed 13 winners against Zvonareva and six against Kvitova, who respectively hit 49 and 36 in reply, while making considerably more unforced errors than the Dane.

They both know that tennis is a game of calculated risk-taking. Those overhead smashes that barely touch the baseline and second serves that you hit just a bit harder than usual make all the difference. But Wozniacki  rarely takes risks. She would appear to be playing every single match with her number one ranking in mind. Her success proves this is working well at the moment, but when will she give herself the chance to improve her offensive game? Because defensive players don’t win grand slams. “You have to win grand slams,” contended two-time grand slam winner Amélie Mauresmo in an interview with Eurosport following the 2011 Australian Open. “They won’t be handed to you.”

It’s also a matter of peaking at the right moment, and this has never been one of the Dane’s strong suits. This year, for example, only two out of her six tournament wins were in premier WTA events, and she for the second successive year failed to make a grand slam final. The Estoril Open is irrelevant when you don’t make it past the third round at Roland Garros the following week, and the truly great players understand this.

The art of peaking is difficult to nail down, because it takes an unknown amount of both mental and physical rest. Mentally, a player needs to be both confident and hungry. Achieving this balance is extremely difficult – when Wozniacki finally finds a coach to replace her father, it needs to be somebody with experience in this area. Multiple grand slam winner Martina Navratilova, who Wozniacki spoke to earlier in the year, would definitely fulfil this criteria.

But maybe all the 21-year-old star needs is a different mentality. It’s easy to become complacent after 54 weeks on top of the rankings. Wozniacki needs to ask herself what it means to be great, and then decide what she is going to do to ensure that she gets there.

With a new mentality and a little luck, Wozniacki is capable of winning the Australian Open in just three months time and bringing home Denmark’s first grand slam since 1957. She can shorten the list of number ones who have failed to win a grand slam to just three. And most importantly of all, she can finally answer that nagging question.

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