A bit of storytelling there with this Ajax youngsters theme. Last season they added only experienced players with Blind (29), Tadic (30), Labyad (26) and Magallan (25), to a side that had played the Europa League final in 2016-2017. Most youngsters were not making their debut but had been playing for three or even four seasons together, more or less since the EL final season. The exception was Mazraoui who really came on stage last year and played a lot right away.
Last season, the most used players for Ajax were Blind (29), Van de Beek (22), Tadic (30), De Ligt (19), Onana (23), Schöne (33), Neres (22), Ziyech (26), De Jong (22), Mazaroui (21), Tagilafico (26), Huntelaar (35), Dolberg (21), Labyad (26), Veltman (27), Sinkgraven (24), which illustrates that those young players were surrounded by well seniored players. So apart from Mazraoui, it's six field players + one goalkeeper as already used youngsters, who had all been involved in the Europa League Final and had already a decent number of professional games under their belt before last season : Onana (123 pro games + best African goalkeeper 2018), Van de Beek (116 games), De Jong (83 games), Dolberg (77 games, youngest non-Dutch player to score a hattrick for Ajax), De Ligt (62 games), Neres (54 games). Ajax did not throw in young players all at once last season, which surely makes a difference because they had a far more difficult season in 2017-2018 and even 2016-2017 when the Europa League final kind of saved their season.
Man Utd youngsters will be guided by which senior players, esp. if Sanchez leaves as well ? Mostly De Gea / Romero, Young, Mata, Smalling, and maybe Maguire / Lindelöf. Pogba wants to leave and seems more interested by himself than people around him, Matic is the shadow of himself, Fred's not really made it. Those Man Utd youngsters should be brought into the team with caution and benevolence, not like the whole team relies on their offensive performances.