His 'philosophy' all the way through his entire career has been about bringing young talent through. Yes, injuries have meant that we've relied on these kids playing...but, again, this is the what the contingency plan has been. There were plenty of people surprised that we didn't sign more players, people concerned that our squad was too small. But this has been his plan right from the beginning.
And injuries haven't been the sole reason why some of these players have had a chance. Lingard, for example, would have been a key part of United's season last season if his knee hadn't exploded against the Swans during the first game of the season.
All of those players I've listed are quality players. They won't ALL make it at the highest level at United but Rashford, Fosu-Mensah, Borthwick-Jackson, both Pereiras and McNair most certainly will do.