"It is a great shame for Florent," manager Sam Allardyce told the club's official website.
"He has had a setback to the original injury and is finding it difficult to stand up to the physical demands of The Premiership.
"It could be a while before he is back in the first team but he is working hard to get back on the park as soon as possible.
"It's important that he doesn't rush and we'll make sure that the timing is right before he starts playing again."