The agent of Porto goalkeeper Iker Casillas admits his heart attack came out of the blue.

The Real Madrid legend suffered a heart attack during Porto training on Wednesday and has been operated on to resolve the problem.

"Iker felt ill halfway through training," Carlo Cutropia told El Partidazo on COPE. "His chest, his mouth and his arms were really hurting. He wasn't conscious when he had the heart attack. He was told afterwards.

"He'd never had a single symptom and there will be no effects. Iker had all the luck in the world that it happened during training in front of the Porto medical staff. If that it'd happened at home, the consequences would've been unpredictable."

The former Real Madrid captain is in a stable condition and spent Wednesday night in hospital.

"By the afternoon, Iker was the Iker that we know: making jokes, happy," Cutropia said. "He's a fighter, because he's not going to play again...

"This is more important than winning the World Cup. It's the best victory of his life.

"Today Iker made the save of his life."