Juventus coach Massimiliano Allegri accepts it will be "difficult" for Cristiano Ronaldo to return from his thigh injury in time to face Ajax in the Champions League quarter-finals next week.

Ronaldo sustained the problem during Portugal's 1-1 Euro 2020 qualifying draw against Serbia last Monday and missed the slender 1-0 win over Empoli on Saturday.

Allegri and club chairman Andrea Agnelli insisted the 34-year-old would not be rushed back earlier than necessary, with Juve 15 points clear at the Serie A summit.

It had been suggested Juve were planning to keep Ronaldo out of league games against Cagliari and AC Milan before bringing him back into the fold for the April 10 trip to Ajax.

But it now seems Ronaldo could also miss the first leg of the Champions League last-eight tie in Amsterdam.

"Ronaldo is working and we hope to have him for Ajax, but it will be difficult," Allegri said at a news conference. "We hope he can [play], he is working every day.

"Today's [Monday] examination is much better, the leg is better. There are nine days left until Ajax and we have time to evaluate. We must be careful and evaluate.

"As for Douglas Costa, he's in good condition and should be available for Ajax. [Sami] Khedira has worked with the team and could to be there for Milan.

"Paulo Dybala will be evaluated to understand how he is doing with the knock on his shoulder. He will not play in Sardinia [against Cagliari on Tuesday] and we hope to have him back to face Ajax."

Although Ronaldo's injury leaves Juve short in attack, it has given highly rated youngster Moise Kean an opportunity to impress.

The 19-year-old scored his first two goals for Italy during the last international break, and, having scored the winner against Empoli, he is set to start against Cagliari on Tuesday.

"We will see what he gives on the pitch," Allegri said. "He is young, he has enthusiasm and he is fine. It will be a good test for him, against a tough team.

"It is a test for his growth. He is 19 and has important qualities, we hope to continue like this and he will surely have ups and downs.

"Let's not forget about his potential, he must reach the level of a great team player. He has to come to the pitch every day and work, improve every day.

"If someone is satisfied [with themselves], they are good for a year and then they are lost. I hope that Kean is intelligent to understand that, but that depends only on him."