The Irish defender has suffered a sprained ankle while club physio Alex Manos has also confirmed the player has suffered some ligament damage as well.
This weekend's game against Southampton is a non-starter for the player, while it also looks as though he will be a big doubt for the clash with Liverpool a week later.
"Damien has got a sprained ankle and there is some ligament damage in there," Manos revealed. "At the moment he is in a protective boot, we are trying to settle it down and let it heal. So he is not available for the weekend.
"He is doubtful for next weekend. We'll try and see if it is possible to accelerate his rehab but we're probably looking at after the Liverpool game."
Crystal Palace last week