Spain's World Cup-winning goalkeeper Iker Casillas will be released by Porto at the end of the season as the cash-strapped Portuguese giants look to cut costs.

Francisco Marques, the Porto spokesman told A Bola daily, that the former European champions need to slash the contracts of their best-paid players.

"For example, Casillas's deal ends at the end of the season. It's a very expensive contract," he said.

"We will scrupulously pay his salary until the end of the season. We have no alternative."

"But when the contract ends, it will free-up millions of euros."

Casillas, his country's most-capped player with 167 appearances, had signed a one-year extension to his deal last July having left Real Madrid in 2015.