The 26-year-old France international returned from a 12-week lay-off against Anzhi Makhachkala in Moscow last week, but has sat out the two games since and has now been told he may need an operation.
Manager Alan Pardew said: "Looking at him, I think he's going to need an operation on his hamstring, and it will probably leave him missing for the rest of the year, I think. We have had to absorb that in all the good news that we have had."
- Sports & Recreation
- Anzhi Makhachkala