Manchester United have seen Kobbie Mainoo emerge as a serious first-team star, but not every young prospect at the club can reach those levels. There is a long, long history of Manchester United giving chances to academy players. After all, Ethan Wheatley became United’s 250th academy graduate to make their first-team debut back in April. The ‘Class of 92’ remains a major source of pride and Kobbie Mainoo is now representing the United academy admirably. Mainoo broke into the United side this past season and made himself an almost instant fan favourite. The 19-year-old turned in superb perform…