Petkovic to miss Australian Open

The injury-plagued German was forced to retire from her opening singles match at the mixed teams tournament on Saturday due to a knee problem, having just won the first set against Australian teenager Ashleigh Barty.

Petkovic was in tears as she left the court on Saturday, and revealed on Twitter on Sunday that she had ruptured the meniscus in the knee for the second time in as many years.

She has withdrawn from the Hopman Cup, where she was partnering veteran Tommy Haas and will return to Germany for her rehabilitation.

"So it's a rupture of the meniscus, back to Germany as soon as possible for an arthroscopy," she Tweeted. "Relieved it wasn't the ACL again."

Petkovic, 25, had a reconstruction on the same knee in 2008, after tearing her anterior cruciate ligament in the first game at that year's Australian Open.

She also suffered from ankle and back problems this year as her ranking slipped from a career-high ninth last year to 126.

Because of her low ranking, Petkovic needs to qualify for next month's Australian Open.

Hopman Cup organisers are seeking a replacement for her.