Traore was forced off in Sunderland’s 1-0 win over Leeds earlier this week after coming on as a substitute, having recently returned from a knee injury.
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“The date is not exactly set, but it could be a long injury,” Le Bris said.
“We’re still deciding whether it’s surgery or a more conservative treatment, we don’t know that yet. But yes, he will be without it for a while, I think so.”
Jocelin Ta Bi and Romaine Mundle are likely to be out long-term with injuries, but there were positive updates on Brian Brobbey, Reinildo, Nordi Mukiele and Dennis Cirkin ahead of the FA Cup clash with Port Vale.
“Brian trained this morning; he won’t be available for Port Vale, but next week he should be fine,” Le Bris said.
“Rei should run on grass this weekend, which is also good. He is very close to returning to the team. Everything is going well.
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“Nordi will probably run next week as well. They are in the group to be available in Brighton or Newcastle.
“Dennis, same idea. He ran last week and it still hurt a little bit, but not too much, which is normal. It’s based on symptoms and we still have to adapt the rehab program based on what he’s feeling, but he’s in a good place.”
Goalkeeper Robin Roefs will also be out for about two weeks.