The Black Cats have replaced Robson with Valentino Angeloni and have already begun to reshape their squad, with Valentin Roberge, Cabral and Modibo Diakite all joining the club this week.
Robson, whose playing career took in three stints with Sunderland and included spells with Newcastle United and West Ham United, left the Wearside club after two years in the role at the start of May.
An overhaul at Sunderland has also seen the arrival of new director of football Roberto De Fanti, but Robson fears that the club's new direction may bring more problems for the club that flirted with relegation from the Premier League last season.
"I fear it might happen that Sunderland will concentrate solely on the overseas market," said Robson, 67.
"They might go for cheaper options, younger players, European players, Croatians, Italians - but they still have to be good enough to play in the Premier League, which is pretty demanding.
"But you read where probably Norwich is the only team in the Premier League that is fielding enough of a percentage of English players, and I feel that's a sad situation
"It's a worry to me in the English game. I don't know where the development is going to come from. The Premier League has spent a lot of money on academies but we need to keep working on it."