Eder and Luis Muriel both hit braces in the rout.
“The attitude was wrong from the start in a terrible first half," said Castori.
“We lacked concentration and made costly mistakes. We recovered a little and gave what we could, but I will admit the emotional weight of the occasion was tough to bear.
“I don't talk about individual performances, as collectively we got it all wrong. We improved after the break just out of sheer pride. We scored twice and that penalty could've further reduced the gap.
“Carpi are not the team you saw in the first half. The fightback was a positive sign and we can build on that. It can happen once, but from now on we must have a positive attitude and be aware of our capabilities."