However, Blancos coach told the news conference ahead of Wednesday's trip to Sevilla that he expected all of his players - including now sidelined Isco and Dani Carvajal - to be fully recovered for the trip to Kiev.
"Cristiano is the one to worry about more because it was only 48 hours ago, but he's going well, he's doing OK".
He continued: "I believe that the Argentinian national team without Lionel Messi wouldn't be a contender".
Zidane went on to add he's unsure when Ronaldo will return but reiterated "it's only something small". "Without Ronaldo it would be impossible, but with him nothing is impossible", the Portuguese told ESPN Brasil. The Portugal striker will miss tomorrow's La Liga clash against Sevilla. "It is great that he can walk already and that shows his drive and ambition to get back and play every game".
Ronaldo, scored his 25th goal of the season and 42nd in all competitions, when he cancelled out Luis Suarez's opener, but picked up a knock in the process.
Real booked their place in a third-consecutive Champions League final last week by beating Bayern Munich 4-3 on aggregate.
"That goes without saying", he said after revealing that he wouldn't actually be attending the game himself. The team who will follow their planning in a better way will end up winning the game. His movement was outstanding throughout the first period, and while he got on the scoresheet, latching on to a brilliant Karim Benzema knockdown, he could have easily taken the game away from Barcelona with other chances.