Van Aanholt, who arrived at Selhurst Park in January from Sunderland, picked up an ankle problem in the 2-0 victory at West Bromwich Albion last time out.
The left-back has been ruled out of the game against the Hornets but manager Sam Allardyce is confident the Holland international will return to action after the international break.
He said: "From last time we played, Patrick van Aanholt is our only injury, with his ankle. He’s moving forward quite quickly. Only Patrick missing from the team that played West Brom."
Allardyce also confirmed striker Loic Remy, who has endured an injury-ravaged season, will be missing this weekend although he will be back to full fitness after that.
He added: "Loic Remy not fit yet, he is training, due to join up with the full squad in the international break."
France international Mamadou Sakho, on-loan from Liverpool, is set to partner James Tomkins at the heart of defence whilst Wilfried Zaha and Andros Townsend will set up on the flanks.