United were behind with less than five minutes remaining, due to a virtuosic volley from former Reds hitman Cristiano Ronaldo, but levelled when the Spaniard clipped home after Paul Pogba was fouled on the edge of the area.
“As soon as there was the free-kick in there, I had the confidence that I had to take it," said United's no.8.
“I told Ash: 'Please let me take it, because I can go over the wall.'
“It's very difficult for the goalkeeper because they don't see a lot [with the wall so close]," added Mata, who was voted Man of the Match by United fans.
“So I tried to do what I do in training a lot of times, practicing, practicing. It was important to score to make it 1-1 and, after, it led us to the 1-2. I think because of the venue and the importance of the game, it's one of the best [that I've scored]."