The Portuguese tested positive on 13 October while on international duty and has since been in quarantine at his home in Turin.
Ronaldo’s absence has prevented the highly-anticipated latest instalment of his rivalry with Lionel Messi.
And with both playing in different leagues, it was seen as one of the final occasions to witness the two legendary players go head-to-head.
Both teams won their opening games of Group G, with the Italians beating Dynamo Kiev and the Spaniards beating Ferencvaros respectively.
There will be one more occasion to witness Ronaldo vs Messi when the return leg takes place on 8 December at the Nou Camp.
Ronaldo’s absence has denied Andrea Pirlo the opportunity to showcase his first choice front three.
After signing Alvaro Morata from Atletico Madrid, Pirlo is intent on using the Spaniard alongside Ronaldo and Paulo Dybala.
“We are thinking to play them as a front-three,” Pirlo said. “With Ronaldo in his classic centre-left position”.
While Juventus defender Danilo insists the Old Lady can defeat the La Liga giants without their talisman.
“I feel good about the way we play; we often have the ball and therefore there’s no problem,” the Brazilian said. “I don’t know about tomorrow, but I’m ready to do my best. We have to be quick and focused.
“We are on the right path. These are the best matches to play in. Any team would miss a player like Cristiano, but we have faith in all the players.”