Bayern Munich face starting the season without Franck Ribery after a second examination of his ankle revealed ligament damage.
The 28-year-old picked up the injury in training on Sunday morning and initially thought it was just a sprain.
However, the playmaker was sent to see Bayern's chief medical officer, Dr Hans -Wilhelm Muller-Wohlfahrt, who highlighted more serious damage.
The news will come as a serious blow to both the France international and Bayern.
Ribery was racked with injuries last season and had hoped to enter this campaign in peak physical condition.
He will now have to wear a cast on his ankle for the next five days before being reassessed.
The club face Borussia Monchengladbach on 7th August in the opening Bundesliga game of the campaign.
"The injury is worse than we thought," he told www.bild.de. "I don't know why these things always happen to me.
"I need to wear a cast for five days and then, hopefully, will be able to start running from Monday."