MELBOURNE, AUSTRALIA - JANUARY 19: Ana Ivanovic of Serbia celebrates winning her fourth round match against Serena Williams of the United States during day seven of the 2014 Australian Open at Melbourne Park on January 19, 2014 in Melbourne, Australia. (Photo by Chris Hyde/Getty Images)

Melbourne – Giant-killer Ana Ivanovic on Sunday credited a new-found self-belief for one of the biggest wins of her career after upsetting top seed Serena Williams at the Australian Open.

The Serb, who has never revisited the highs of 2008 when she won the French Open and made the Australian Open final, said she was now more mature after struggling with her fame and fortune early in her career.

“I think all the struggles were just for moments like this,” said the popular 26-year-old, who has family in Melbourne and is nicknamed “Aussie Ana”.

“I actually believed. I had some confidence coming into today's match. I really did certain things extremely well and I kept her under pressure I felt throughout the whole match.

“I just think I stayed in the moment physically. I didn't think much about the occasion and who I was playing, because it can get overwhelming,” she added.

Since winning at Roland Garros in 2008, Ivanovic, now ranked 14, has only made a Grand Slam quarter-final once before, at the 2012 US Open.

But under new coach Nemanja Kontic, the Serb has been thriving and came into Melbourne on the back of winning her 12th career title in Auckland.

She said becoming world number one in 2008 and winning a major was overwhelming for her.

“It's very hard, because for me, I'm still a little bit shy, so for me it was very overwhelming with all the success and attention I got,” she said.

“I kind of wanted to get away from it a little bit. And then when I was away, I didn't want that. I wanted to still work hard.

“But then I was in a little bit, you know, not the best place in my mind. But you just keep fighting because this is what I love to do and this is what I'm best at.”

“But it's just a road, and we all have to pass through certain parts and mature along the way,” she added.

After working with various coaches Ivanovic now has a Serbian team behind her, led by Kontic, who all speak the same language and have given her the confidence she was lacking.

“I have now a Serbian team with me. I'm really happy with the way everything is going, and we did work very hard in the off-season,” she said.

“I really feel that the team that I have now is really behind me and they believe in me.

“I went through the tough times when maybe I doubted, but they don't. That means a lot to me.”

Ivanovic now faces a last-eight clash against either Canadian teenager Eugenie Bouchard or local hope Casey Dellacqua, and she said she can't wait to get back out on court.

“You know, I feel ready, and I want to challenge everyone out there,” she said. “I know there are going to be a lot of tough matches.

“I'm ready for the battle, and hopefully I can show this game all the way.” – Sapa-AFP