IT would be rather unrealistic to have a set date on which your youth players come in. Your scouts go scouting, but know exactly on what day they will find the player they are looking for. Nah, they just have to search until they find what they want.
And that you get your 2nd player late doesn't mean your 3rd will be late too, your 2nd player will probably still be able to get all his 20 matches.