Confident Kerber enjoying the challenges of a World No 1

Angelique Kerber is the world number one in women's tennis yet it remains a title she has yet to grow accustomed to after her meteoric rise to the summit.

Still a relatively new experience, the 28-year-old German reached the peak of the women's game last month after landing her second grand slam title of the year at the US Open, capping a stunning season for the left-hander from Bremen.

Kerber floated around the lower echelons of the top 10 for the last four years and did not even make the second week of a grand slam in 2015, but it all clicked in January.

A run to the final in Brisbane preceded a surprise upset win over Serena Williams to land the Australian Open title as the baseliner renowned for her strong defensive game finally realised her talent.

"All the experience from the last few years came together this year. The belief in myself, I've grown up a little bit more this year," she told Reuters of her new-found maturity.

"The victory in Australia, of course it's great, I continued it the last few months and I'm here now as the best player of the year... and the world actually," she added, chuckling as she corrected herself.

Kerber is guaranteed the year-end number one ranking after Williams pulled out of the $7 million season-ending WTA Finals in Singapore, which starts on Sunday, with a shoulder injury.

Kerber said she would "miss" the 22-times grand slam singles champion but did not offer a similar sentiment for Russia's Maria Sharapova, who is scheduled to return to the circuit in April after her 15-month doping ban expires.

"We will see when she is coming back, I don't know, I'm not thinking about this," she replied, appearing keen to change the subject.

Instead Kerber, the first left-hander to top the world rankings in almost two decades, remains primarily focussed on advancing out of the group stage at the eight-woman WTA Finals for the first time.

Last year, she only needed to take one set from the already-eliminated Lucie Safarova to reach the semi-finals but struggled to contain her frustration and was easily beaten by the Czech to suffer a third early exit in as many visits.

"I learned a lot from this special moment because the pressure was really high for me last year and this year I'm handling (it) much better and this will never happen again," she said.

Kerber, who also claimed an Olympic silver at Rio and was beaten by Williams in the Wimbledon final, has also experienced a few lows in a year of many highs.

She followed up her victory in Australia with a first round exit at the French Open and has suffered surprise early defeats to Australia's Daria Gavrilova in Hong Kong and Elina Svitolina in China this month.

"The pressure is actually bigger... because people expect you to win every tournament," said Kerber, who will treat herself to a beach holiday after the Singapore tournament.

"Nobody has anything to lose against me. And everybody would like to beat me. The pressures are bigger than before but it's a great situation to be in, it's a new challenge for me and I'm happy to be there right now."