Serena Williams knocked out of Australian Open

Women's top seed and world's No.1 Serena Williams was knocked out of the Australian Open in the fourth round losing to Serbia's 14th-seeded Ana Ivanovic 6-4, 3-6, 3-6 here Sunday.

Williams, who was also the top seed in 2013, was eliminated by then-19-year-old fellow American Sloane Stephens in last year's quarterfinals, which was the biggest upset of the tournament, reports Xinhua.

Williams returned with more power to the Melbourne Park as she went 78-4, won 11 titles and became the oldest player to ever rank No.1, all in 2013.

Williams dominated the previous four meetings against Ivanovic and never let the Serbian even win a set. Williams won the first set 6-4 and it seemed like another stroll to the quarterfinals for the five-time champion.

It was the second set that turned things around. Ivanovic hit 15 winners and dominated with her first serve. Williams struggled with her first serve for most of the match and Ivanovic pounced on every second serve to give herself the advantage in points.

"I made a tremendous amount of errors and I missed shots I normally don't miss. Shots I haven't missed since the 80s," said Williams.

"I definitely didn't feel myself today."

"Serena is such a great player. Going on to the court today, I really just tried to give my best. I tried to make it a good match," said Ivanovic.

"I was very competitive till the last moment, and I'm just very thrilled, obviously."

Ivanovic reached the final here six years ago but lost to Maria Sharapova. She then won at Roland Garros.

Ivanovic will play the winner between Aussie wildcard Casey Dellacqua and Canadian Eugenie Bouchard in Tuesday's quarterfinals.