Success in Europe has been more forthcoming for Zinedine Zidane's side, though, with a comprehensive 5-2 aggregate victory over Paris Saint-Germain in the last 16.
And Karembeu believes the two-time defending champions are the only side left in the competition who can win the title – despite Barca, Manchester City and Bayern Munich joining them in the quarter-finals.
"Don't even ask the question," the former Madrid midfielder told Omnisport, speaking courtesy of Hublot.
"Only Real can win it [the Champions League], that's it.
"In Kiev, who's going to play against Real, this I don't know. Real will be in Kiev, yes."
And Karembeu – who won the Champions League twice with Madrid – was just as positive about Zidane's prospects in coaching, despite him coming under pressure at the Santiago Bernabeu.
"He was an amazing player and he will become an amazing coach," he added. "He's doing it already."
Zidane is not the only French coach Karembeu is a fan of, the former midfielder backing Didier Deschamps and Les Bleus to bounce back from their Euro 2016 final disappointment at the World Cup in Russia.
"France will win because 20 years ago we did it," he added. "Didier Deschamps is experienced and knows his group.
"They played a final of a European Championship at home.
"He saw some interesting performances. It was a successful competition. He has to bounce back."
One thing the 47-year-old is not looking forward to in Russia is the introduction of VAR, Karembeu believing errors made by officials should be accepted as part of the game.
"Obviously, we live in a new generation," he said. "If we have to implement new technologies we have to accept it, but again, we have to remain human – errors are human.
"We are allowed to let the referee make some mistakes. He's just like us. A player is also making mistakes. Why not the referee?
"We'll always speak about the 'Hand of God' of Maradona. Football is theatrical, it's a show."