The France international was substituted with a minor knock to the leg against Bournemouth last time out but should have recovered in time for the arrival of the Hornets.
Meanwhile, Joel Ward is a doubt with a groin injury, which will come as a blow to manager Roy Hodgson with the wing-back impressing in recent weeks.
Hodgson also confirmed on Monday that centre-back Mamadou Sakho will be out "for a long time" after injuring his calf and will play no part against Watford, who have impressed the Eagles boss so far this season.
He said: "I will give you three things that are good - their athleticism, their work rate and the quality of their individual players.
"We are preparing for the best Watford team we have seen. They have done very well and they are ninth because that is what they have deserved."