Those twin successes, Real's first such double since 1958, were built on the strength of a powerful squad which allowed coach Zinedine Zidane to frequently rest regulars without a drop in results, but his squad at Wembley looked remarkably thin.
In the summer, Real parted ways with Colombia's 2014 World Cup Golden Boot winner James Rodriguez, Spain striker Alvaro Morata, fullback Danilo and veteran defender Pepe, bringing in youngsters Theo Hernandez and Dani Ceballos.
Their starting 11 on Wednesday featured 18-year-old Achraf Hakimi and second choice goalkeeper Kiko Casilla, while the average age of the team's substitutes was 20-years-old.
"The players who have arrived have a lot of potential but Pepe, Morata and James made us stronger and the players are younger now," Ronaldo told reporters after the defeat.
"Our squad isn't worse, but it's less experienced and experience is very important. But it's no excuse and we shouldn't be alarmed."
The front cover of Spanish newspaper Marca on Thursday was at odds with Ronaldo's reading of the defeat. "All the alarms are going off," it said, adding "Madrid's domestic crisis is transported to Europe".
Daily AS headlined its edition "Nightmare at Wembley".
Real only need one more point from their last two games to qualify for the last 16 but must win both matches and hope Tottenham drop points twice to avoid coming second in the group and drawing a group winner in the next round.
Ronaldo dismissed any talk of a crisis at Real, pointing to the team's enormous success under Zidane, with whom they have won seven trophies in under two years.
"People forget about the good times very quickly. I never talk of a crisis, you can lose three or four games but there's never a crisis. We can't forget what we've achieved," Ronaldo added.
"This is a bad run but we want to turn things around and I'm sure we will. This is only the start of the season, we still have a lot of time to improve and I'm convinced we will."
(Reporting by Richard Martin; Editing by John O'Brien)
