FIFA Women's World Player of the Year Nadine Kessler is a major doubt for Germany's Women's World Cup campaign as she requires surgery on a long-standing knee injury.
Wolfsburg midfielder Kessler has not played since October due to the issue.
The 26-year-old will now certainly miss the rest of the domestic campaign and, although no date has been put on a return, she faces a race to be fit for European champions Germany in time for the World Cup that starts in Canada in June.
"I regret that Nadine has to be operated on again," Wolfsburg coach Ralf Kellermann told the club's official website.
"She is a real leader, which is very important for the team both on and off the field. I hope that the operation is successful and she will be able to start training soon."