The striker has battled to get off the bench this season.
Allegri said: “Dybala is calm, he's trained well in the last week and as I've has tomorrow he could play from the first minute again.
“The relationship with him absolutely hasn't changed, also because Dybala came to Juventus three years ago and I think he's grown a lot, Juventus put even more emphasis on his qualities and he's given a lot to Juventus.
“In my opinion, he still has huge margins for improvement. The comparisons which were made at the start [of the season] were damaging for Paulo, but fortunately he's a smart lad and he understands you can't compare a lad of 24 to two sacred monsters of football [Messi and Cristiano Ronaldo], who have won 10 Ballons d'Or.
“Plus there's Neymar who is another that is close. So Paulo has to make his own way and not be compared to any other player.
“He has his own qualities, he's an extraordinary player. You just have to watch him to see he's different from the others.
“But these comparisons which were made were a bit damaging, these are comparisons which can not and should not be made, you can't compare a 24-year-old lad to two who have won 10 Ballons d'Or. But in Italy…
“It's not just Dybala, Dybala is the least of that problem. There are lads who play half an hour and the next day they're worth €40m."