While Terry went on to win the Premier League title and captain his country, Percassi slipped away from London after two first-team matches. He quit soccer at 23 after several stints at clubs in Italy's second tier.

"The only regret is that I left too early because I became homesick," said Percassi, who completed an economics degree after finishing his professional career. "Maybe if I could have stayed there I would have had more chances."

English teams can sign players to professional contracts at 16, while most other leagues, notably those in Spain and Italy, are bound by rules making it difficult to offer professional terms until 18.

Percassi has never been back to Chelsea, preferring to follow his friend Terry's successes from afar.

"I played next to him and I could see he would be a great player at 16 and 17. When I saw him become England captain I said, 'I'm so happy for him,"' Percassi said.

He doesn't see his English experience as a failure and would counsel others to follow the trail he and other Italian youngsters mapped out in the late 1990s.

"I had the chance to improve my personality and to learn about a new country, a new language and a new culture," he said, speaking in English laced with colloquial terms picked up from Chelsea's training ground.

Eric Harrison spent more than 20 years coaching youth teams at 17-time English champion Manchester United, bringing through the likes of David Beckham, Ryan Giggs, Paul Scholes, Nicky Butt and the Neville brothers, Gary and Phil.

He's unconvinced by Chelsea's headline-grabbing signing of Boga. Talent at 12 doesn't always mean a successful professional career, he said. More than 90 percent of youth players training with professional clubs in England drop out.

"If he's the next Zinedine Zidane that means he's going to be a world-class player, an international player — if anybody can tell me that about a 12-year-old, I think it's absolutely crazy," Harrison said.