Hannover midfielder Leon Andreasen has been dealt a major blow by tearing his cruciate knee ligaments in Wednesday's game against Nurnberg.
Andreasen was carried off the field after less than 10 minutes, with the diagnosis arriving after a scan on Thursday.
The Dane arrived in Hannover from Fulham in 2009, but a series of injuries culminating in a groin problem forced him to miss a total of 28 months before returning towards the end of last season.
He now faces a further six months on the sidelines.
"This is a bad diagnosis for Leon, who has an eternity of injury misfortune behind him," said Hannover's coach Mirko Slomka.
"I wish him all the best from the bottom of my heart. This also hurts the team since we have to replace a really strong player."
Hannover's director of sport Jorg Schmadtke has no doubts that the 29-year-old will return after his injury stronger than before.
"I know him and that he will work passionately on his comeback," he said in a club statement. "He has immense will and the strength to suffer."