Mata was a guest on a recent show, talking about the weekend's Premier League game with Chelsea and his former teammate and current Blues coach Frank Lampard.
"From the first day I walked into the Chelsea locker room, I felt that he was a very smart person. He knew everything about football. As a player, he had a deep understanding of football. You can imagine that he will become a very Good coach, just like he does now."
But as an opponent, Mata knows that Lampard's team can cause trouble for Manchester United in the weekend game.
"Of course we know that Chelsea is dangerous because they signed a lot of good and important players. They are a very strong team both offensively and defensively. So we know their strength and we need to be prepared for it. "
"But we also have to consider that we are playing at home. If we play at our own level, we will create scoring opportunities and have the opportunity to take all three points. Of course, they are very powerful opponents to us because we are competing for the same Something. It will be very important for Chelsea to win, even though we know it is difficult."