Ronaldo, who was suspended for Tuesday's Champions League win over Young Boys, has "firmly denied" a rape allegation after Kathryn Mayorga accused the Portuguese of sexual assault in a Las Vegas hotel in 2009.
The forward called the claims "fake news" and then issued a further statement on social media in which he strenuously denied the allegations and called rape "an abominable crime".
Both Juve and Ronaldo's international head coach Fernando Santos have offered unwavering support to the 33-year-old, although he was left out of the Portugal squad for the upcoming matches against Poland and Scotland, and Allegri has confirmed he is available to face Udinese.
"I've known Cristiano for three months now and for over 15 years of his career he has shown to be a great professional both on and off the pitch," he said at a news conference.
"He is ready to return to action tomorrow.
"He agreed with the coach of the national team not to go. He has broad shoulders, is focused for tomorrow and to do well, external things do not affect him.
"Cristiano is calm, his professionalism inside and outside the camp is indisputable."
This week Las Vegas police reopened an investigation into alleged sexual assault from the same year as Ms Mayorga's allegation, but they have not named either the victim or any suspects.
Ms Mayorga's attorneys held a news conference on Wednesday in which they outlined the emotional impact they say their client has suffered as a result of her alleged assault.
German publication Der Spiegel first reported the claims, prompting Ronaldo to stress his innocence.
"I firmly deny the accusations being issued against me," he posted on Twitter.
"Rape is an abominable crime that goes against everything that I am and believe in. Keen as I may be to clear my name, I refuse to feed the media spectacle created by people seeking to promote themselves at my expense.
"My clear conscious [sic] will thereby allow me to await with tranquillity the results of any and all investigations."
"Cristiano Ronaldo has shown in recent months his great professionalism and dedication, which is appreciated by everyone at Juventus," the club said in a statement.
"The events allegedly dating back to almost 10 years ago do not change this opinion, which is shared by anyone who has come into contact with this great champion."