Hazard was on the receiving end of a clumsy challenge from his international teammate, Thomas Meunier, in the Champions League clash between Real Madrid and Paris Saint-Germain, but the French coach had hoped it was only a minor ailment.
Initial reports from Madrid suggested that it was just a very badly bruised ankle, however fears resurfaced on Wednesday evening when the former Chelsea playmaker arrived to the player's Christmas function on crutches.
A fresh medical examination was thus required, and it has shown Hazard to have suffered a stress fracture in his right ankle, which means he definitely won't play at the Camp Nou.
Zidane himself was cautious on his assessment of the injury in the wake of the draw with PSG, however he has suspected since that night that the forward wouldn't be available for selection until the new year.
With this absence now official, the Frenchman can now start to game-plan for the Clasico in the knowledge he will have to make changes, and it's expected he will utilise a 4-4-2 formation with Gareth Bale and Karim Benzema in attack.
Furthermore, Marcelo is also a doubt for the match after he suffered a muscle injury in his calf, but further assessment is required.