Eriksson had admitted that he had not seen some of the eight players he signed in the summer in a £40million spree funded by controversial new City owner, former Thai Prime Minister Thaksin Shinawatra, play many live games.
But two of them, £8.8million Italian striker Rolando Bianchi and free transfer Brazilian Geovanni, scored the goals which demolished dismal Hammers - and left the Upton Park fans applauding Eriksson.
"Okay, I haven't seen all of them play nine or 10 times but I have big scouting staff at the club and I have as many videos as I need to watch.
"I've always signed good football players. And with these ones, some are young and for the future and some, like (Martin) Petrov and Elano, are more experienced."
It was Elano, another Brazilian who cost £8million from Ukraine's Shakhtar Donetsk, who starred in City's stylish performance as their new-look team - with eight debut-makers - repeated the win they had at West Ham last December and doubled the scoreline.
He made a storming run and cross for Bianchi's 18th-minute opener and often ran West Ham ragged in his support striker role.
But he had been substituted when compatriot Geovanni clinched the three points with a rifling strike three minutes from time.
Eriksson, brushing off questions about whether he enjoyed club football more than his ill-fated England reign, declared: "England is history for me today. I don't think I had a player like Elano with England.
"We are playing a different way with Manchester City. It is a big club and the aim is to make it much better.
"The owner has not asked me to win the Premier League - not this season anyway - or get into Europe, but we will see where we are when the squad is fully ready."