If you were to walk past Simona Halep in the street, it is unlikely you would think you had just crossed paths with a world-class athlete.

With her slight frame, the Romanian looks smaller than her 5ft 6in but when the Australian Open begins in Melbourne tomorrow, it is she who presents the biggest threat to the established elite.

Suggesting Halep as a threat for Grand Slam glory is hardly a massive leap of faith with her ranked No 3, not least since she reached the French Open final last summer. The 23-year-old is among the fittest players on the Tour and a gifted mover, but has added more power to her game in recent times.

Serena Williams remains the favourite to win a sixth Australian Open, while Maria Sharapova, Petra Kvitova and Agnieszka Radwanska are all high on the bookmakers' list. But what Halep lacks in stature, she more than makes up for in confidence and having shaken off a stomach problem, she believes this could be her time.

"I'm much stronger than before," she said after another training session at Melbourne Park. "My game is complete now. I believe in my game."

Halep hit the big time when she reached the final in Paris last June and though she was overpowered by Sharapova, the experience convinced her she belonged at the top.

"I didn't expect that I could play finals after just one quarter-finals in a Grand Slam," she said. "But, you know, I had nothing to lose there. It was my favourite tournament, because I had won in juniors, and I feel very well there. I was trying everything on court.

"Then I had in Singapore the second big result [reaching the final of the WTA Finals]. I played well there. I cannot say that I was surprised, but still I was very happy at the end of the year that I did have big results."

Halep is no longer an unknown quantity and the chances are that the likes of Williams will step up their efforts should they face her in Melbourne. But going from the hunter to the hunted does not seem to have unsettled Halep; in fact, she loves it.

"It's better than last year. I can say now I feel no pressure," she said. "I have just to play my game and to see how good I can be, how many matches I can win."

Unlike many of her fellow players, Halep prefers the cold to the heat, which doesn't bode well for Melbourne where temperatures can be extreme. Having a roof over the three main courts will help her chances and she doesn't feel she missed out on anything by not getting some warm-weather training under her belt.

"I have played in Shenzhen," she said, referring to the Shenzhen Open, which she won. "It wasn't too hot there. That was a good thing for me. I like to train in snow, when it's cold outside. I just had my own preparation. I prefer to stay home, stay close to my family, to recharge my batteries. I was 20 days practicing in the snow and I was running a lot."

Williams began 2015 by winning two and losing two of her singles matches at the Hopman Cup, a mixed-team exhibition event in Perth. A week in Melbourne has improved her mood, although she said there was still work to be done if she is to be in the hunt for a 19th Grand Slam title.

"I definitely feel better now than I did a couple weeks ago," she said. "But I still want to improve some things."

Having dominated the event between 2003 and 2010, winning five times, Williams has not gone beyond the quarter-finals in the past three years.

"It would be really great [to win]," she said. "I've been going for number six for a number of years now. It would be really special for me. I want it I think more than anyone else here. But that doesn't mean I'm going to get it, so I'll have to fight hard."