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.
Alan Pardew: "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.
"That's the priority for him now because he's been a huge miss for us.
"He gives us that X-factor. In a game like last night's where he could open the door for us, we haven't got that luxury.
"Unfortunately for Hatem, that's the news that he didn't want to hear. But as far as we are concerned, the team has responded well in his absence and hopefully, we do that until the end of the year."