Mata conceded that he had been liberated by Di Matteo after spending the first two thirds of the season in a starting role on the left, which he did not entirely enjoy, under Andre Villas-Boas.
Mata, whose controversial goal in Sunday's FA Cup semi-final win over Tottenham was the 12th of his first season in English football, said: "I feel comfortable on the pitch now because I can move freely.
"I wanted to be able to find spaces between lines, turn around with the ball and have time to think about what will hurt the opposition.
"In my mind, I am not a winger. So when I am able to come inside, I feel I have a better view of the pitch and what I want to do with the ball.
"Over the last few games I have given quite a few final passes which have led to goals."