Ronaldo worked separately from his team-mates on Wednesday after picking up a knock in last weekend's 1-0 win over Bologna but did return to full training the following day.
Juve's commanding 13-point lead over Napoli - their nearest challengers in the table - prompted suggestions the Portuguese could be rested from Sunday's meeting as Allegri's men look ahead to a Champions League last-16 tie with Atletico Madrid in 10 days.
The Bianconeri trail 2-0 from the opening leg in the Spanish capital and will surely need Ronaldo at the peak of his powers to have any hope of a turnaround, but Allegri dismissed the notion of resting his star man for the visit to Napoli.
"Ronaldo trained with the team and will play tomorrow," Allegri told a news conference on Saturday.
"Sami Khedira needs tests. We hope to get Douglas Costa back against Atletico Madrid, but Juan Cuadrado is still a long way off recovery."
The loss in Madrid, as well as Juve's surprise Coppa Italia elimination at the hands of Atalanta in late January, has seen the Serie A champions come in for what Allegri believes is unwarranted criticism.
"I was disappointed by the reaction, because people had created some expectations Juventus had to go to Madrid and beat Atletico 3-0," he said.
"It's not an intelligent assumption, not one for people with their feet on the ground.
"These are expectations based on something that is entirely outside of reality. We were missing four important players. You can lose one game and make up for it in Serie A over the next 12 rounds, but in the Champions League you can lose once and that's it, you're out.
"I understand constructive criticism, but not when expectations are beyond reality. It is not normal to win, it is always extraordinary and must always be treated as such. If you don't, then that's not my problem.
"Let's not forget in my tenure, Juventus lost 11 games in the Champions League, including ones against Young Boys and Sevilla where we were already qualified, Manchester United in bizarre fashion, then Barcelona, Real [Madrid] and Atletico. I am not a fan of statistics, but that's an impressive statistic.
"I was angry with the way we lost to Atletico Madrid, but I was angry with myself, not with the critics. I am the coach and set the example, but I also have to be accepted for who I am.
"We should focus on Napoli, a stadium packed with people eager to beat us. We must play with intelligence, sharpness, intensity, clear heads and knowing it's never over at the San Paolo."