Ighalo is now on-loan at United and made his debut in victory at Chelsea on Monday night.
Marino told TMW, "It's an operation that pleases us.
"It means that choices made at the time were suitable. He was valued by Watford, we are pleased that he has reached such great levels."
"He is doing well. You can see his hand. It was a brave choice, time will prove us right. He made himself available, it was more a journalistic thing. The team has great empathy," he added.