He plays 3 positions, RB where Darmian and Valencia play naturally and Jones and Young can cover so he would be at most third in the depth chart there. DM where Carrick, Schneiderlin and Blind play and if everything goes in order Pogba can play too so that's 4 players in front of him in the depth chart. He also plays CB where Smalling, Bailly, Blind, Jones and Rojo if Jose doesn't sell him (if he sells him he will probably buy an experienced center back ), so he is there 5th in the chart but competing for 2 places even though i really doubt that Mourinho will play so young player in a position he values so much as a core of his team. So that means if he stays he will play 10 games at most all season. I'm not an expert and i don't know what he will benefit more: training with the first squad and play few games, learning from Mourinho in the process or going on a loan where he will play more regularly in a team like Burnley for example, but i think he should go somewhere and become a regular first team player for a season.