Mata was handed a place in the starting XI for Manchester United’s 2-0 win over Swansea and produced a characteristically crisp display on the ball.
Martial, on the other hand, has been linked with a move away once again having only made two starts since the January arrival of Alexis Sanchez.
But the 22-year-old appeared to be in good spirits alongside Mata in the pool ahead of Saturday’s trip to the Ethiad Stadium.
Mourinho noted ahead of Man United’s win over Swansea that he chose Alexis in order to configure the tight spaces in the final third left by the visitors, and nobody can argue that it didn’t work: alongside Mata and Jesse Lingard, the Chilean ferociously manipulated the space between midfield and defence to pull them out of shape.
Against Man City, however, the dynamic will be entirely the opposite. United will be playing the Swansea role, so to speak, ensuring every possible channel through which City build momentum is shut down and relying on quick counter-attacks to create chances.
Surely the raw pace of Martial, possibly as a strike partner with Romelu Lukaku in similar fashion to how United set up at the Emirates in December, would provide a genuine test for Vincent Kompany and Co on a day where the visitors simply cannot afford to lose.