Monaco midfielder Joao Moutinho is to miss a minimum of three weeks of action with an ankle injury.
Mourinho suffered an ankle ligament sprain in Friday's goalless draw against Lille, and will now miss his side's Champions League playoff against Valencia.
The Portugal international is also a doubt for Monaco's league meeting with Ligue 1 rivals Paris-Saint Germain, as well as his country's games against France and Albania early next month.
The 28-year-old joined big spenders Monaco alongside James Rodriguez in 2013 in a combined deal worth €70m (£49.7m).
