Ronaldo limped out of Portugal’s 1-1 Euro 2020 qualifying draw against Serbia on Monday with an injury to his right thigh, which will definitely rule him out of Sunday’s Serie A game versus Empoli.

While Juve enjoy a 15-point lead at the top of the domestic league table, losing their top scorer for the Champions League quarter-final first leg at Ajax on April 10 would be a much bigger blow, with the second leg in Turin following just a week later.

But Allegri cautioned that if the 34-year-old had not won his fitness battle by then, there was no way he would be risked.

"He will have tests on Monday, we'll evaluate things from there," Allegri said on Friday, AP reported.

"There is a risk — and a lot of risk — that he will miss the match against Ajax, he knows it, too, and he knows, too, that if he is not fit then he will stay out."

"Ronaldo is fine, he started moving again yesterday a bit, but caution is needed because it's best to miss one match than the end of the season," Allegri added.

"We are in a delicate phase; he will return when he is well and there will be no danger that he may have a relapse."

Ronaldo will miss the Empoli tie and potentially Serie A games against Cagliari away and AC Milan at home, but the club boast a potent attacking threat with the likes of Mario Mandzukic and Paulo Dybala.  

Juventus president Andrea Agnelli noted that the squad has considerable depth in the attacking department.

"Juventus has the good fortune to have an in-depth squad," Juventus president Andrea Agnelli said.

"Cristiano is the best player in the world, if you have him on the pitch he gives you an extra sense of security.

"That said, when you have muscle injuries you have to be very careful. For one match you risk compromising the next two months. ... It's more important to safeguard two and a half months than one match only."

Ronaldo’s goals helped Juve into the Champions League last eight, as he netted a hat-trick in the last round against Atletico Madrid to overturn a 2-0 first leg deficit.

The Portugal star was handed praise from an unlikely source on Friday, when Barcelona rival Lionel Messi admitted he misses not playing against the former Real Madrid talisman in La Liga.