The title favourite led Stephens by a set and a break, but went down 3-6 7-5 6-4 after leaving the court to be treated for a back spasm in the second set.

If Williams had won the 2013 Australia Open, she would’ve reclaimed her number one ranking. This is the first time she’s ever lost to a younger American.

Microphones on the court picked up Williams saying it had been the “worst two weeks”. She sustained an ankle injury in the first round and had been dealing with back pains.

“I’m almost relieved that it’s over because there’s only so much I felt I could do”, she told the BBC. “I was unaware the microphones picked that up.

“But, it’s been a little difficult. I’ve been thrown a lot of balls these two weeks”.

Williams, 31, is said to have cried out in pain while rushing for the ball at 4-3 down. The doctor took her off the court, but when she returned, she was unable to play at her best.

Early in the third when it was clear the lead slipping away from her, Williams threw her racquet to the ground and hurled it towards her chair, which resulted in a code violation that cost her $1,500.

After she won, an exuberant Stephens said in a courtside interview, “Oh my goodness. I’m sure my grandparents are freaking out. I’m sure they’re watching on the computer”.

As the 29th seed, Stephens is now on the brink of entering the ranks of the world’s top 20. This is her first Grand Slam quarter-final. She’ll next play the defending champion Victoria Azarenka of Belarus in the semi-finals on Thursday.

Meanwhile, Williams is left to wonder “where is the love”?

Image via AP.