After playing a big part in their fourth-place finish at the World Cup, Alli featured in the Three Lions' UEFA Nations League opener against Spain on Saturday.
He could not prevent his team from going down 2-1 to Luis Enrique's men, but Cascarino hopes he used the occasion to study Isco in action, as the former striker believes the Madrid playmaker should be Alli's role model.
“Dele Alli is a phenomenal talent, has performed at the highest level and is still only 22, but I think he's now facing the first battle of his career," the ex-Chelsea, Marseille and Northern Ireland star wrote in The Times.
“He burst onto the scene with his skill, flair and ability to make runs into the box and get important goals.
“I want to see Alli put himself about the pitch, making more challenges, and improve his passing game because at the moment I don't think he's a guaranteed starter for Gareth Southgate.
He added: “Alli should look at Isco for Spain, he controlled the game, always wanted the ball, made the right decisions.
“Even when Isco is not scoring or making assists he is affecting the game. Yes he has more experience but that is what Alli should be aiming for.
“Alli's position in England's midfield is key if they are to push on to the next level.
“He has the ability but managers will not wait for ever for him to fulfil it."
Alli has made 150 appearances for Spurs since joining in 2015 from MK Dons, where he impressed in over 70 League One matches.