Ronaldo, 35, missed a penalty and spurned several chances against Milan in the 0-0 draw but the Bianconeri still managed to advance to the final on the away goals rule.
Their opposition, Napoli, who ousted Internazionale 2-1 on aggregate were distracted by a training ground incident with club-record signing Hirving Lozano will be aiming to spoil the party and in pursuit of their sixth Italian league cup.
Juve head coach Maurizio Sarri suggested the three-month lay-off may have contributed to Ronaldo's poor display and touched on his struggles to thrive as a centre-forward alongside Paulo Dybala.
"He doesn't miss many penalties. This one was quite unfortunate and he probably struggled because of that," Sarri explained in the pre-match press conference, as per Sky Italia.
"We discussed it with him and he was completely open to the idea [to move away from the left-wing role].
"He's such an extraordinary player that I don't think it changes anything for him whether he plays five meters ahead or behind. He can play any of the forward positions."