The Serbian picked up a knock during the 4-2 win over Watford last week but was passed fit at the last minute to feature against Arsenal.
Mourinho prompted major concerns soon after the win by noting that Matic was once again injured and wouldn’t play a part against CSKA Moscow.
But the 54-year-old, speaking soon after the 2-1 win over CSKA on Tuesday, confirmed that the midfielder would play for sure on the weekend.
Mourinho: 'Matic is injured but will play for sure [vs City].' #mufc
— Samuel Luckhurst (@samuelluckhurst) December 5, 2017
Losing Paul Pogba for the derby was bad enough; to see Matic miss out as well would be nothing short of unthinkable.
His presence in the middle will be invaluable on Sunday. Without Pogba, the Portuguese is likely to push his wing-backs high up the pitch and use a midfield bloc comprising of Matic, Ander Herrera and possibly Marouane Fellaini as well to keep track of Kevin De Bruyne and David Silva in the centre whilst the raw speed of Romelu Lukaku and Anthony Martial puts Vincent Kompany under pressure.
And, just like at the Emirates, none of this will work without the 29-year-old diligently stamping out fires at the base of proceedings. This is a man whose career has been largely built upon nullifying mesmerising, fizzing attacking midfielders and, needless to say, he will need to be at his commanding best on Sunday.
Mourinho on Man Utd's injured players' chance of playing v Man City: "Eric Bailly no chance for the weekend, Phil Jones a chance, Fellaini a chance, Zlatan a big chance and Matic is injured but will play for sure. Carrick, no chance."
— Richard Jolly (@RichJolly) December 5, 2017