Casillas: Champions League tops the World Cup
Casillas, who won the World Cup in South Africa in 2010, was very nearly Real's villain in Lisbon, as he conceded the game's first goal to Diego Godin in the first half of the European final.
The 33-year-old came to collect a loose ball, however he was lobbed by Godin's header - and despite his desperate attempts to keep the ball out, Diego Simeone's side led.
However, the shot-stopper's blushes were spared, when Sergio Ramos equalised in stoppage time, before goals to Gareth Bale, Marcelo and Cristiano Ronaldo sealed Real's 10th European cup.
Casillas, Real's captain, claimed their success was more important than achieving success with Spain in Brazil.
"This is more. It's so important, it's more than the World Cup," Casillas said, as reported by Sport.
"It's been so long, the 10th, it's a round number, a perfect number.
"I want to congratulate those who have come here and thank the fans who have not said anything bad.
"We suffered. They got a fortunate goal when we made a mistake.
"They had more chances and we have kept coming several times. We suffered more than necessary into added time.
"On occasions it seems a fair result. They defended well, killing time at the end, but we did it.
"It's what we have. We fail, we succeed. Hopefully people will remember the 10th was won in Lisbon. Sometimes we fail, other times we hit and I can't complain."