Manchester United booked their place in the quarterfinals of the Europa League on Thursday, with a 1-0 win at home to Rostov sufficient to ensure a 2-1 aggregate victory.
While Sunday's trip to Middlesbrough is their only game remaining before a two-week worldwide break, they are already without the suspended Ander Herrera and Zlatan Ibrahimovic heading to the Riverside.
United have the upper hand against Rostov, having netted an away goal in a 1-1 draw in last week's last-16 first leg in Russian Federation, but their heavy schedule means freshness remains a concern.
And on 70 minutes, United finally managed to find a way through when Ibrahimovic flicked a Mkhitaryan cross into the path of Mata at the far post, who fired into an empty net from just a few yards out.
The same pattern resumed with the Reds in complete control of proceedings but Rostov nearly took a surprise lead when dangerman Sardar Azmoun struck a fierce effort from the edge of the box which Sergio Romero repelled before the keeper fielded another shot from Miha Mevlja.
United felt they should've had a penalty after 27 minutes when Medvedev seemed to shove Henrikh Mkhitaryan after the Armenian midfielder went to head the ball inside the area, yet the referee was unmoved as United's players and fans protested.
Mourinho was scathing about the surface, which had large bare patches, ahead of his team's 1-1 draw with Rostov in the Europa League last week.
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United heeded the warning and pressed hard for the opener, with Ibrahimovic heading over from Antonio Valencia's cross.
Eric Bailly could come back in to the team alongside Chris Smalling after missing the first leg through suspension with Phil Jones the man likely to make way at the back.
Match-winner Mata told BT Sport: "It was a matter of finishing our chances again". The Swede has scored seven goals in his last eight games, he got a hat-trick in United's last Europa League home game, and I fancy him to step up again.
If Rostov progress, they will be the fourth Russian side to reach the quarter final stage of the Europa League since 2010/11 (Spartak Moscow 2010/11, Rubin Kazan 2012/13 and Zenit St Petersburg 2014/15).
The score remained goalless as the sides entered the halftime break. The Reds then travel to lowly Middlesbrough on Sunday 19 March for a crucial League match in which three points must be earned.
Subs not used: De Gea (GK), Young, Carrick, Lingard, Rashford.
Subs not used: Goshev (GK).