If Xavi gives every new player a chance to show himself, Barcelona will never regain its former power. The problem is that to understand whether the player has adapted, whether he shows his level of play or not, you need at least a few matches, that's a lot. I think he will assemble a team of players in whom he is confident and who are time tested
When it comes to giving new players the chances to show case themselves, it often comes out beautifully because, you would see them putting in there all in the team to make every effort count. There might be some flaws due to inexperience because that does work too but fir sure, there all would be show cased on the pitch. To enable them win a first team shirt or at least be on the bench. You can take a look at Arsenal and its young team, they might not be the best in there prospective league and are weathered by inexperience but, they are doing ther quarter and it's helped them to the Europa qualification.
I think if new players are given chances they should be given only one instruction above all and that is ""
go out there and show what you can do"".
Because that is the only way a young player is going to play really fearless football, if a young player is given too many tasks to do and think on the football field he will surely end up not performing at his best potential in my opinion.
So, while experimenting with young players I think they should be given the freedom of expressing themselves on the field. And through that, the football world might find something very beautiful.