Serena Williams is not only formidable on the tennis court but also in business

SHE is the best in the world on the tennis court but Serena Williams has proven she is also a formidable businesswoman.

Serena Williams in Berlei.

SHE is the best in the world on the tennis court but Serena Williams is a formidable businesswoman.

The 32-year-old has two clothing lines and spends hours building a fashion empire.

"Fashion is my life outside of tennis,'' she told the Herald Sun yesterday.

"I do a tremendous amount of work with both of my collections, and now working with Berlei, it's lots of fun.''

The tennis player is a hands on ambassador for the Aussie brand Berlei, shooting a campaign yesterday afternoon in Collingwood.

The world No.1 had a phenomenal start to 2014, defeating Victoria Azarenka in Brisbane to win the title last Saturday.

Relaxed and content with her small entourage around her that includes her mother Oracene Price, coach and rumoured boyfriend Patrick Mouratoglou, Williams and company stay at a South Yarra hotel and she isn't shy about exploring the city.

Serena Williams models the new Berlei sports bra she helped design.

She played her first Australian Open in 1998 and over the years she has grown to love the City.

"What's not to love about Melbourne?" she said.

"I love the city, it's one of my favourite stops of the year.

"I have so many friends here.

"I've been coming for so many years so it's great to see so many people you can truly call friends.''

Williams has a kitchen in her hotel room but she will be still checking out the Melbourne's restaurants.

"I love seafood and we have a kitchen so I'll probably be doing some cooking this year,'' she said.

"I love French restaurants as well.

"Melbourne has so many restaurants and great shops, good designers, there is so much inspiration from fashion to food.''

Perhaps in a warning to her rivals, she said she is feeling super fit leading into next week's Australian Open.

"I definitely feel better,'' she said.

"At the end of last year I felt a little tired.

"I was a little concerned about that, I felt my technique was struggling a little bit.

"I was like, oh my gosh, I hope this isn't from fatigue.

"But I feel like I'm continuing on the up and am not tired.''