The Spaniard replaced Adnan Januzaj just after the hour-mark and drove home in the 67th minute to wrap up the three points for the Red Devils at Old Trafford.
Mata hit the post with another effort later in the game but his goal proved enough to secure victory for Louis van Gaal’s men.
The victory hoisted United up to sixth place in the Premier League table, but still left them 13 points behind leaders Chelsea, who were 2-1 winners at Anfield earlier in the day.
Next up for United is a trip to Arsenal after the international break on 22 November.
Here are some of the best pictures from Saturday’s Premier League clash at Old Trafford.
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