Both teams meet at Old Trafford as the Portuguese boss looks to get his Europa League campaign back on track.
Martial suffered a knock at Vicarage Road in a collision with Daryl Janmaat and was then involved in the incident that led to Watford’s opener seven minutes later.
Speaking in his press conference, Mourinho revealed Martial has now recovered.
“He’s now recovered from the contusion – not the concussion,” he said.
“He has recovered and he is ready for tomorrow.”
Martial was fouled in the lead up to Etienne Capoue’s goal and was left on the floor for several minutes before being escorted off the pitch.
He has missed the League Cup tie at Northampton on Wednesday and Saturday’s visit to Old Trafford of champions Leicester City, but will hope to finally return to action.
The Frenchman hasn’t looked the same under new boss Mourinho so far but hopes are once he finds his feet on the side, he can continue from where he left off last season, following a spectacular debut season.