"I don't think Savio is a gamble for me," he said. "I know what he can do. I have to add something to his game but I'm sure he's not a gamble.
"With the qualities he has got we will find a place to put him in.
"We have expectations of him but he is 19 years old. He has come here for the future. He has great potential and can become a top player. But the crowd and everybody need to be patient with him.
"We are going to help him to improve but he needs some time to settle down."
Nsereko, who admitted playing for Zola was one of the big attractions in coming to London, said: "It is a big responsibility, but I know what I can do.
"I'm happy to be here and proud to have the possibility to play for West Ham. I know a lot about the manager. I saw him play and he was a great player and a great manager also."
Zola insisted there were no plans for any more departures from Upton Park following Hayden Mullins' move to Portsmouth.
He said: "There were a lot of rumours that we would not be able to buy anybody and only be able to sell but I'm working with a club which is run by good people and they want to improve the club.
"They are not worried about investing money we got from the transfer window to take the club forward."