McCarthy played for Mourinho at Porto.
"Mourinho's one of these people who thinks, 'if you throw a punch at me, I'm going to throw two at you'. He threw two knockout punches at Wenger," he told talkSPORT.
"I know him very well and, for him to lose it like that, is because Arsene started the whole thing. He's just responding to Wenger's comments. He can be very sarcastic when he wants to be."