Ronaldo tussled with Jeison Murillo and appeared to put his hand on the centre-back’s head in the 29th minute inside the box, with the official behind the goal signalling for an offence.
German referee Felix Brych consulted with his assistant and opted to send the Portuguese star off.
A tearful Ronaldo left the pitch in disbelief but Allegri maintains he would have avoided a red card if UEFA had opted to approve the use of VAR for Europe’s premier club tournament.
“I can only say that VAR would have helped the referee make the right decision,” Allegri said. “Mostly because it was the 29th minute in the first half in a difficult game, to find yourselves with 10 men for a red card, that was not right.
“It could have complicated the situation for us, but the guys have been very good. They played well as long as they had to, until (we were) 2-0 and then we defended with order, leaving them a few shots on goal, but nothing special.”
Despite Ronaldo’s dismissal, Juventus recorded an impressive 2-0 win at the Mestalla Stadium, with Miralem Pjanic scoring twice from the penalty spot.
That leaves them second in Group H behind Manchester United, who sit top after beating Young Boys 3-0 in Bern.
Juventus face Young Boys in Turin next, on October 2, before back-to-back games against United and Allegri feels his side have put themselves in a strong position.
“We will play Young Boys at home and in theory we should defeat them,” Allegri said. “These three important points, which allow us to face the group in a different way, but we still have to win the matches that are left.”
It remains to be seen whether Ronaldo will miss the fixtures against United following his red card.
He is certainly out of the game against Young Boys. A red card in the Champions League results in an automatic one-game ban with no right of appeal.
Further punishment is at the discretion of the UEFA Control, Ethics and Disciplinary body.
UEFA regulation 50.01 states: “As a rule, a player who is sent off the field of play is suspended for the next match in a UEFA club competition (i.e. UEFA Champions League, UEFA Europa League or UEFA Super Cup).
“In case of serious offences, the UEFA Control, Ethics and Disciplinary Body is entitled to augment this punishment, including by extending it to other competitions.”