Mata moved to United from Chelsea in 2014 after three successful years at Stamford Bridge.
“I have always felt good at United but obviously in these years the club have not lived the best moment of its history,” he told IBT.
“When you are in a team that may not have met the group targets it seems that everything has less impact.
“But in terms of stats, feeling an important player for the team or enjoying my football I feel as good as when I arrived to Chelsea.
“What happens is that in Chelsea we won the Champions League, the Europa League and the FA Cup in two years.
“Obviously that highlighted everything more than when you are in a club that is not winning much.
“But last year we already won the FA Cup and hopefully this season we can win another cup.”