Casillas was speaking in his new Movistar+ documentary series Catching the Wings in comments carried by Marca.
The series is distilled into six episodes from over 300 hours of footage and featured over 30 interviews with people important to his life and career.
“There is a sensation of half a second, or not even that, when you take a breath of air and it tastes different,” Casillas said.
“I noticed that I felt heavy and short of air, and I began to think it might be an allergy. Then, when I went to the goalkeeping coach, I felt my chest begin to tighten and I noticed that I was running out of air.
— Movistar+ (@MovistarPlus) November 27, 2020
“I told him, ‘Roberto, give me sugar or something because I feel wrong and I don’t know what’s wrong with me’. I lay down on the ground and I could see something serious was happening to me.
“It’s like you’re in a pool and suddenly you want to get out and you can’t, it was an anguish. I was getting more and more short of breath. ‘Robert, please call the doctor,’ I said. ‘I’m drowning’.”
— Fútbol en Movistar+ (@MovistarFutbol) November 27, 2020
Two months after suffering the heart attack in the May, Casillas was back at pre-season training with Porto.
He retired at the end of the 2019/20, and is now reported to be working in an advisory role to Florentino Perez at Real Madrid.
Aside from his five years with Porto, Casillas spent his entire 22-year senior career with Madrid, 16 of which he spent as Spain’s goalkeeper.
Casillas won five La Liga titles, three Champions Leagues and one Primeira Liga, amongst many other titles, at club level.
With Spain, he was an integral part of the side that won two European Championships and the 2010 World Cup.
Featured image courtesy of the Daily Advent Nigeria.