Mata grabbed a double, but United ended up ceding more ground to Manchester City in the title race after a 2-2 draw yesterday.
And after scoring his second goal in the 60th minute, the Spaniard produced a prayer symbol.
Supposedly he made the gesture after visiting a group of children from the OSCAR Foundation who travelled from Mumbai to visit him at Old Trafford.
Explaining the celebration, Mata said: “It was because when the kids from the OSCAR Foundation that we work with for Common Goal came to Old Trafford to visit me, they asked if I could do this kind of celebration for them.
“For the first goal, I didn’t do it because we needed another goal but, for the second one, I thought about them and this goal was dedicated to those kids in Mumbai.”
Mata was left disappointed after the draw and admitted it felt more like a defeat: “You have to keep going, particularly at Christmas time when you play every two or three days.
“Now we feel frustrated and angry, but we need to keep going and from tomorrow, rest and think about the next game.
“Obviously we aim to finish the next one with a much better feeling.”
United are currently 13 points behind league leaders Manchester City.
They face Burnley next on Boxing Day (3pm).