Dier reckons boss Jose Mourinho's perfect mix of seriousness and smiles is a key factor in Tottenham 's early-season success.
The Spurs defender, who started his career at Sporting Lisbon, said: “It has been incredible to be able to work with one of the best managers of all time.
“Obviously, the connection we have with Portugal is also special for me and so in that sense it has been fantastic to learn from him and work with him.
“We're obviously just at the beginning of our journey but it has been fantastic.
“He's extremely serious and professional when it comes to work and I'd say he's the first to be serious when it's time to be serious, but he's also the first to have a laugh and a joke when it's time for that as well.
“He can do both and always in the right time.
“Having someone who has been there and done it on so many occasions on the biggest stages obviously carries a lot of weight in the dressing-room whenever he does speak and whenever he expresses his opinions towards how he feels we need to change to do better, to be able to go to that next step.
“Obviously everyone's ears are open because his resume speaks for itself.
“So whenever he speaks on anything, everyone is paying a lot attention to it.
“He also gives us a lot of confidence as well because he obviously has all the titles to back it up, so you really believe in it."