Serena Williams knocks out World No. 1 Simona Halep in Epic Australian Open clash

Serena Williams reached the quarterfinals of the Australian Open after surviving a severe test against world No. 1 Simona Halep.

The American dropped her first set of the tournament and was pushed all the way by the Romanian in a thrilling match which ended 6-1 4-6 6-4.

It had all started so easily for the American. Williams wrapped up the opening set in just 20 minutes, dropping just one game to the struggling top seed, but the Romanian fought back to setup an enthralling decider.

Serena Williams reached her 50th career Grand Slam quarterfinal.

'I just never give up'

Both women came out swinging to produce one of the most entertaining sets of this year's tournament, with each having chances to break serve. But, like is so often the case, it was Williams who dug deepest to make the breakthrough.

"I'm such a fighter, I just never give up," the 37-year-old said to the adoring crowd during an on-court interview. "It's definitely something that's innate. I just work so hard for every point."

The 23-time grand slam champion has now won nine of her 10 matches against Halep and outlined exactly why she's favorite to add an eighth Australian Open title to her career tally.

Simona Halep was an unlucky loser in the wonderful match.

'A miracle that I'm here'

The American has not won a grand slam since she returned from pregnancy last year but is just happy to be back playing her sport.

"It's a miracle that I'm here," she said, before joking about how her daughter's love for Disney films keeps her up at night.

"I get to do something I enjoy. This is my job, my job is to come out and play in front of you and that keeps me motivated to keep trying and keep fighting for literally every point."

Williams will now face Karolina Pliskova in the quarterfinals after the Czech breezed past Garbine Muguruza in straight sets.