The South Africa international said: "Without him, the League is a bit sad. He is special and he was always interesting, a great coach, as we now recognize.
"At this point, few coaches make a difference. Of course there is Ferguson, Wenger, Benitez, Hughes, Keegan, but someone like Mourinho is difficult to find. He is of a higher level because players were dying for him. This is something very difficult to find.
"He's left a big gap, because he was the only one who could take the spotlight from Sir Alex Ferguson."
McCarthy, who played for Mourinho at Porto, added: "Even if people do not want to admit it, everyone has missed him."