Paulo Dybala came off the bench to inspire a 3-0 Serie A victory, setting up Gonzalo Higuain and scoring the third himself.
Allegri stated, “Dybala is improving a great deal and has everything it takes to become, along with Neymar after Cristiano Ronaldo and Leo Messi, one of the best players in the world.
“His future is with Juventus and I am very happy with that. Over the last three years we've done well and we have an important campaign ahead of us too.
“Douglas Costa has to get to know his teammates and settle in. I always say it's tough to play in Serie A, as the small to medium clubs are very organised and close the spaces with intelligent tactics.
“I think Douglas Costa would've done great things in the final half-hour when the spaces opened up, so he has to make an impact during the opening hour when there are very few spaces.