Going to be tough for him to break through as we have a lot of options in those wide/number 10 positions and they're all guys who are unlikely to leave this summer. Martial, Rashford, Lingard, Mata, Mhiki are the attacking midfielder options you obviously assume Rooney will be leaving but there will probably be a striker coming in the summer so competition is fierce in these positions but the benefit he has is a lot of these guys aren't putting up the numbers if he can get a chance and score goals/create chances I don't think Mourinho has a problem putting youngster in. However, they have to deliver straight away you won't get 10 games to ease into it you need to make a pretty instant impact in a Mourinho side.
We also have Januzaj to come back who's a similar type of player my personal opinion is that he will probably be sold this summer and I think it's likely that Periera will go out on loan again hopefully this time to a club in England either in the PL or Championship.
He got a bit stitched up in the summer he was due to go to Fulham on loan but they have a stats analysis department who blocked the move at the last minute because his numbers didn't add up despite the manager wanting him so he kind of got farmed to Grenada at the last minute they're a poor side in La Liga but the reports that I read are that his talent stands out and he's scored a couple of nice goals as well.