Juve signed Ronaldo from Real Madrid with a view to him spearheading their charge towards European glory but the 34-year-old is yet to scale his usual heights.
An expert volley against former club Manchester United in the group stage is the star forward's only Champions League goal this term and his hopes of lifting the trophy for the fourth straight season will be extinguished if the Serie A champions fail to overturn a 2-0 deficit on Tuesday.
Atletico are favoured by many to protect that commanding first-leg advantage in Turin but Ronaldo, the competition's all-time leading goalscorer, shapes a pivotal figure in deciding which team advances to the quarter-finals.
Bianconeri boss Allegri is adamant his marquee acquisition will rise to the challenge.
"Because it is an important match and he is exalted in competitions like this," Allegri told reporters.
"He's scored only one goal, but with [the red card against] Valencia he has played just five games.
"He has scored so many goals [throughout his career] in the Champions League and having him with us is a great advantage.
"Everybody has to give something more tomorrow. They have to give 100 per cent. That is, to do what they do best."
Allegri's men rode their luck for long periods in the first leg at the Wanda Metropolitano before succumbing to late goals from Atletico defenders Jose Gimenez and Diego Godin.
Alvaro Morata had a goal ruled out via VAR in an impressive cameo off the bench in that match and heads back to face his former employers with three goals in his last three La Liga appearances.
Juve captain Giorgio Chiellini revealed he and his team-mates were disappointed to see the striker leave Allianz Stadium upon his return to Real Madrid in 2016.
"Morata is a great guy," Chiellini said ahead of his 500th appearance for the Italian side.
"We were all hoping that he would stay here. Tomorrow we will have to be wary of him as well as [Antoine] Griezmann and Atletico's other players."
The hosts will be without Douglas Costa for the clash after the exciting attacker sustained in a setback in his recovery from a muscle issue.