Maurizio Sarri is delighted with Juventus' form but acknowledges the team must be better than in seasons past if they are to again retain their Serie A title.

The Bianconeri defeated Roma 3-1 in the Coppa Italia quarter-finals on Wednesday, scoring through Cristiano Ronaldo, Rodrigo Bentancur and Leonardo Bonucci before half-time.

It was a fifth win in a row in all competitions for Juve, in which time they have built a four-point lead over Inter at the top of the league table.

Sarri saw evidence of this winning mentality against Roma but acknowledged improvement was required in a three-way title tussle with the Nerazzurri and Lazio.

"Winning is becoming normal," Sarri explained at a post-match news conference. "I'm happy for the team.

"But we don't have to look at the numbers because it will be more difficult this year. We will certainly have to do better than previous years if we want to be competitive in the league."

Ronaldo took his 2020 tally to seven goals in four games, and Sarri lauded his "extraordinary" talisman while again repeating a desire to help the Portuguese secure individual honours.

"Ronaldo is in extraordinary physical and mental condition," the head coach said. "He is continuing at an impressive pace and has extraordinary skills.

"He is very well physically. In terms of explosiveness, he is good. He takes great care of the details.

"Ronaldo is a champion, we want to help him win the sixth Ballon d'Or, it would make us all happy."

Juve's next league task takes them to Sarri's former club Napoli, who are struggling in the bottom half of the table.

"It will be a difficult game. We must not look at their position in the table," Sarri added. "They have a strong team. They are going through a difficult time but have good players. 

"From one point of view, there are three points at stake. From my point of view, from a personal point of view, it will be particularly special because I am very close to Napoli."