The influential defender has missed more than a month with nerve damage but now that an operation is required he will not be available until the New Year.
Fulham boss Rene Meulensteen said: "Brede is a bit of a disappointment to be honest, because we have looked at all medical strategies and it's a bit of an awkward one.
"He's seen another surgeon and a specialist and I think they have decided that they're going for the surgery, which will keep him out for at least six weeks. But on a positive note we know now, there's clarity.
"And the one thing that I want for such an important player for us, is that he can focus on the rehabilitation so when he comes back he will be like a new player for us."
Meulensteen is hoping Philippe Senderos will beat his thigh complaint in time to face Aston Villa in Sunday's Sky Live lunchtime clash.
"Phillipe gave a monstrous performance (against Tottenham), he had a bit of a thigh strain," he said.
"But the way he played himself through it was characteristic of the performance, and I paid him a big, big compliment about that. Darren Bent is not allowed to play because of the loan deal."
You can catch all the action from Craven Cottage live on Sky Sports this Sunday, with coverage underway from 12.30pm.