That's an excellent match from him and it was Modric-esque in terms of his playing style. From what little I've watched of him, his two-footedness, composure in crowded areas and how he isn't fazed by players pressing him is rather impressive. He's got the technical ability and creativity but also the grit and a fair bit of maturity (on the field) to go with it.
Interested to see what Jose does with him but it seems likes he's been trying to mould him into a deep lying playmaker of sorts. If memory serves me right, Mourinho played Pereira as the deepest midfielder in the last pre-season's friendlies too. Might be reading too much into that, given how it's nothing more than a run-out. However, perhaps he sees the tenacity and the industrious nature of Pereira and has him down as a deputy for Carrick, and boy have we been struggling to replace him. Now a deep lying playmaker instead of a more robust defensive midfielder might go against Mourinho's typical template, but iirc he did recognise the calming influence and importance of Carrick, and wasn't afraid to try Herrera as the deepest midfielder on a couple of occasions.
Whether Pereira has the tactical discipline and defensive nous for such a role is up for debate, and I see more of a Modric/Herrera sort of an all-round and dynamic creative midfielder as opposed to an Alonso or a Busquets for that matter. I know Pereira has played a variety of roles for Granada but did he ever play the deepest role, and if so, how did he fare? Hopefully, his versatility means he gets his fair share of chances and in quite a few roles. I recall us missing Pogba's creativity when he was out or at times overusing Herrera during the latter stages of the season, so there would be more than enough opportunites for him imo.