Matic, who arrived at Old Trafford from Chelsea at the start of the season, was substituted after 55 minutes of United's 4-2 win at Watford in mid-week with Mourinho saying the Serbia worldwide had a muscular problem.
"I think I will always try to play the best possible team", he said.
"He is selected to go". I hope he can.
"So, for me, you can say what you want, you can analyse in the perspective you want to analyse".
Jones (thigh) has been out of action since limping off in the first half of England's match against Germany on November 10.
And Mourinho subsequently hit out at England's treatment of the player, specifically that Jones had been given six painkilling injections in order to feature in a friendly.
Mourinho also confirmed defenders Eric Bailly and Phil Jones are not available for selection after missing their last three league matches due to injury.
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Southgate added: "We have got ongoing dialogue over this situation".
The fact that the 29-year-old will be traveling to London might indicate some hope. Arsenal have the quality to unpick most sides, especially with Mesut Ozil in good form, but the Portuguese will know that, eventually, frustration will creep in, the Emirates crowd munching their gourmet pies with growing anger, and that is when gaps start to open up, mistakes are made, and the entire atmosphere - both on and off the pitch - becomes toxic for the home side.
The Old Trafford boss revealed that he watched the new film Borg McEnroe on Thursday, and likened United's title chase to a match between the two tennis greats.
Asked if he saw the Arsenal match as "must-win", Mourinho said: "I play a game at a time and I think that's the way to do it".
"Yesterday, I was watching an interesting movie: Bjorn Borg versus John McEnroe".
"And I tell my players, "Think just about the game". It doesn't matter what comes after, or what happened before.
"I play a game at a time, I play a game at a time and is the way to do it, is the way to do it", he declared. So now it is Arsenal.
So yes, he will have a plan to win at Arsenal - but not one that will have changed just because leaders City are eight points ahead of him.