Mbappe trained with the Blues for a week as a 13-year-old and played in a junior fixture, impressing coaches with his talent.
But according to Boga, the Premier League club were unconvinced by his work-rate and asked him to come back for another trial, a request his mum Fayza Lamari rejected.
Boga told Goal: “I brought him over with his family.
“He was skilful, like he is now. He played against Charlton and won 7- 0.
“After a week at Chelsea, we went into the office. We said, “Listen, we appreciate what we saw from you but we have to invite you back for another trial and we’ll see after that.”
“I remember what the mother said to this day. She spoke in French and I was translating.
“She said to me, “Listen, my boy won’t be coming back. If they want him they have to take him now or in five year’s time they will be coming back to buy him for €50million!”‘
Boga, who refused to translate Fayza’s warning to his Chelsea colleagues, added: “He was very skilful but in England they want to see the player track back and be a hard worker. At the time, he wasn’t a hard worker.
“Defensively, he wasn’t there yet. When he got the ball, he was unbelievable, but without the ball, he didn’t work a lot.
“Chelsea wanted to see him again to see how he could improve on this. I think that’s why they asked him back. He did skilful things and dribbled well. So, maybe the thing they wanted to see in the second trial was improved work on the defensive side.
“They should have signed him. To be fair, though, it is easy to say that now. But, at the time, Chelsea had a good squad.”
