Andrea Petkovic has withdrawn from the Australian Open with a stress fracture in her lower back that could keep her sidelined for two months.
The 24-year-old German player was seeded 10th at the Australian Open, which begins Monday at Melbourne Park. She announced her withdrawal on Twitter early Wednesday.
''Sorry to announce that I had to withdraw from the Australian Open with a lower back stress fracture,'' she wrote. ''Going back home, will miss my Aussie fans!''
Petkovic lost 7-5, 6-4 to Agnieszka Radwanska of Poland in a second-round match at the Sydney International on Tuesday. She needed an injury time-out during the match to receive treatment from a trainer.
In a statement released through the WTA, Petkovic said she'd been having back problems for three or four months.
''I've been struggling with it, but I've always believed it was going to be fine and so I pushed through the pain,'' Petkovic said. ''The last two weeks in Australia I've been having bigger problems; I could only play for 30-45 minutes without pain. After yesterday's match against Agnieszka I decided to have an MRI and a CT and the results showed a stress fracture in my lower back.
''The only thing I can do right now is rest - not walking or sitting a lot - just lying down and hoping that the bone will heal as fast as possible.''
Petkovic said doctors advised her it will take six to eight weeks to recover. She was planning to return to Germany on Wednesday night.
''I'm positive this is going to be fine; I just need to take the time off to get better,'' she said. ''I'm really disappointed because I love Australia. It's funny, I actually tore my ACL here, but on the other hand I also made my first ever Grand Slam quarterfinal here. So either it's a big high or a big low!''
Petkovic is known for her celebratory dance after she wins matches - a hip-shaking wiggle that has pleased tennis fans but often irritated her opponents.
She was coming off her best year in 2011, advancing to the quarterfinals of the Australian Open, French Open and U.S. Open and the third round of Wimbledon.
When the seeds were announced Monday for the season's first major, all of the top 32 women had entered the tournament. Petkovic's injury will mean a change in the seedings, with former French Open champion Francesca Schiavone of Italy taking the German's spot at No. 10.
There are also injury concerns over 13-time Grand Slam winner Serena Williams (left ankle) and defending Australian Open champion Kim Clijsters (hip) after both withdrew during the Brisbane International last week.
Venus Williams, the elder of the Williams sisters, pulled out of the Australian Open on Monday, prolonging her absence from the WTA tour because of an autoimmune disease that can cause fatigue and joint pain.
The seven-time Grand Slam title winner was unseeded for Melbourne Park.
