Serena Williams was a shock loser at the Australian Open, stunned by Ana Ivanovic Reigning Australian Open champion Victoria Azeranka has qualified for the round of 16 by easily beating Yvonne Meusberger of Austria 6-1, 6-0. Serena Williams of the U.S. reacts after losing a point to Ana Ivanovic. AN ailing Serena Williams nearly forfeited her Australian Open fourth round yesterday without hitting a ball. Williams revealed a back injury restricted her movement in the shock 4-6 6-3 6-3 loss to Serb Ana Ivanovic before a stunned crowd on Rod Laver Arena. The five-times Australian Open singles titleholder said she also nearly didn't take the court before her 6-3 6-3 win against Slovak Daniela Hantuchova in the previous round. And it prompted her to pull out of the doubles with elder sister Venus before the opening round. It's not like I gave her the match. I tried to fight the best I could today. But, yeah, I almost didn't play," Williams said. But, hey, I did, and at least I feel good that I tried the best that I could on this day. In Williams defence, she did try to conceal the injury that was confirmed by her coach and boyfriend Patrick Mouratoglou. 1 hadn't conceded a set to Ivanovic in their four previous matches. "Well, I guess the secret is out, but I obviously wasn't hitting the way I normally would hit and wasn't moving the way I normally would move and making a lot of errors that I normally would not make and I haven't made in a couple of years," she said. But it's OK I feel like I know for a fact I can play so much better than what I did today. So with that, knowing that, I'm not disappointed or anything. I just know that I can play ten times better than what I did today. I almost pulled out. I'm such a competitor. I mean, I probably should have. Like I said, again, I don't want to blame anything. I feel like Ana deserves all the credit. I feel she played unbelievable today. I think she went for her shots. I have just been on some of the strongest meds I can take that are legal. My body didn't handle it well because I haven't been taking anything. So I was like really kind of out of it for a few days. Williams wouldn't disclose the nature of the ailment that apparently restricted her neck and back, but assured that it wouldn't affect her schedule for the year. I mean, it's not anything that's life threatening or anything. I feel like it will get better. I just need a couple days off. Unfortunately, I don't have that in a grand slam. It will be OK, though," she said. The 17 times major winner said the loss would spur her to work even harder, like the Wimbledon fourth round loss last year. I always feel like I can do better and how I can improve. You know, as I fell at Wimbledon, I was able to get myself back up," she said. Like I said, sometimes it's good when I lose because it takes my head out of the clouds. Not that they are ever there, so to speak. I just work as if I'm ranked 1000 in the world. Williams vowed to return to chase a sixth Open crown at Melbourne Park next January. I feel like I'll win it again. I made a tremendous amount of errors, shots I haven't missed since the '80s," she said. I'm always disappointed when I lose, but it's always a good thing. I plan on getting better. I think it's almost good that I lost today because now I know what to work on, I know what to do when I get on the practice court. It's not easy, you know, playing such a champion ... but she is also just a human and I know she has lots of pressure, too. Ivanovic said. I just went out there swinging at the ball. Ivanovic had 33 winners, including 20 on her forehand side. Williams hit 22 winners but made 31 unforced errors. Australian Open Tenns Day 7. Serena Williams vs. Ana Ivanovic on Rod Laver Arena. Ivanovic celebrates her 3 set win over Serens Williams. Pic Michael Klein. The other quarterfinal will feature two women who'll turn 32 next month, with two-time finalist Li Na beating No. 22 Ekaterina Makarova 6-2, 6-0 and No. 28 Flavia Pennetta upsetting No. 9 Angelique Kerber 6-1, 4-6, 7-5.