Dier admits the Spurs boss Mourinho boasts a major "presence".
He told the Daily Mail: "The manager carries a huge presence.
"His success in the game is something this club hasn't seen so he carries a lot of weight. In the dressing room we're all trying to get to the place where he has been before. And the truth is he is actually the first to be serious when it's time and the first to have a laugh when it's time.
"[Sergio] Reguilon has already said that. So I am stealing his line. But it is perfect because it's exactly right."