The Portuguese superstar departed the Santiago Bernabeu in the summer of 2018 after nine goal and trophy-laden years.
Filling his shoes was always going to be an impossible task for those left behind, but the Blancos have made a mess of their first campaign without the five-time Ballon d’Or winner.
Capello believes their struggles can be explained by the loss of a fear factor which surrounded them during Ronaldo’s time in the Spanish capital.
The former Real boss said at the World Soccer Congress: "I always say that Real Madrid and Barcelona start matches winning 1-0 and if you want to beat them you have to score at least two goals.
"This year Madrid have lacked the 1-0, and have started at 0-0 like the others and that's why they have faced so many difficulties.
"Now we see what is happening at Juventus with Cristiano as, with the Portuguese, the opposition defenders were very scared before and now they are not."
Three managerial changes have been made, with Julen Lopetegui and Santiago Solari both appointed and dismissed within a matter of months.
The reins have since been handed back to Zinedine Zidane, with the Frenchman returning to a post he only departed in the same summer as Ronaldo left.
Capello admits he was surprised to see an iconic figure from Madrid’s past agree to take on a challenge that is considerably bigger than the one he was first handed back in January 2016.
"[Zidane's return] has surprised me a lot to say the truth," said the Italian.
"I think that now he has more power than before, because when he joined the club for the first time it was Florentino Perez who put him on the job and now it was [Perez] who asked him to go back.
"Zidane is the one who knows about the transfers, as there are three good players they can sign and they know who those players are."
Madrid are expected to be busy in the summer transfer reshaping a squad that is considered to require major investment.