That is according to former Chelsea midfielder Thorgan Hazard.
He signed for the Blues along with his brother, Eden, in 2012.
But after various loan spells, Thorgan sealed a switch to Borussia Monchengladbach in 2015 and has proved his worth to the Bundesliga outfit.
Reflecting on his failed spell with the Blues, he told Belgian paper Het Niuewsblad: “I knew I would not stay at Chelsea when I signed for them.
“It was a great opportunity to join such a big club, but I knew I needed regular playing time to show what I could do.
“Chelsea like to buy young players and then slowly get them ready.
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“All the young players like Kevin de Bruyne, Charly Musonda and Romelu Lukaku were shipped out on loan.
“You need regular playing time at that age.
"Maybe Chelsea now regret their decision not to give De Bruyne and Lukaku more chances, I don't know."
Chelsea resume Premier League duties away to Middlesbrough on Sunday (4pm).