Youth Center and disappearing young players

Yesterday I has 3 young players on 8th day, today only one of them left. What is the reason of that? I thought players are 15 days in youth center? Something changed? If yes why only one left, and what is more, the worst of them?

Youth players between 15 and 17 age can stay in youth centre and get be trained there.

if a player is 18 years and in youth centre yiu can lose it if yiu dont promote it.

Zbiciu

Yesterday I has 3 young players on 8th day, today only one of them left. What is the reason of that? I thought players are 15 days in youth center? Something changed? If yes why only one left, and what is more, the worst of them?

@Zbiciu someone else signed them, and they have been replaced