Years after leaving Real Madrid after a tenuous run with the club, Mourinho rekindled his row with Casillas now that the Spaniard has since moved on to Porto.
The Portuguese boss' main qualm: the lofty wages Porto are paying Casillas. According to the Daily Mail's Adam Shergold, the club will be paying Casillas £1.7 million per season.
In Mourinho's defence, he didn't just lambast Casillas' salary. He was also critical of the £14 million Porto shelled over to Marseille for Giannelli Imbula and the big fee paid by Manchester City for Raheem Sterling.