The Portuguese coach made recovering Alli's form of old one of his top priorities when taking over from Mauricio Pochettino last week and it is already paying dividends as the England worldwide has now scored three times in three games under Mourinho.
Two similarly impressive seasons followed, but Alli was not at his best during Pochettino's final year in charge, contributing just five Premier League goals.
"He plays in a position where he feels happy and comfortable", Mourinho said of Alli.
Moussa Sissoko also got on the scoresheet after a fine display, showing his attacking prowess. The best thing that can happen to a coach is when you don't need to speak about a player because everybody speaks - all of you, fans - everybody speaks about him and speaks about him for the right reasons. He's playing really well.
"I felt the boys felt a bit exhausted after playing a high intensity game, but we had the chance to score the fourth goals, but then in the Premier League the game is always alive". He's scoring goals, assisting, working, fantastic. A player of this kind cannot fail at a high level. Normally there's a bit of up and down but you have to perform to your potential.
"Sometimes they are not at their best level but then I find him a good guy in the group".
Starting with the football itself, Mourinho's first three matches have thrown up scorelines more commonly associated with a manager such as Kevin Keegan.
Alli's new role is not dissimilar to the one he was given during his inaugural season at Spurs in 2015/16, where the former MK Dons man enjoyed the ideal breakthrough campaign, notching up 10 goals and nine assists as he scooped the PFA Young Player of the Year award.
Mourinho has been told that funds are available for rebuilding come January, but the former Manchester United boss has taken a restrained approach to gauge what areas require rebuilding and shoring up.