I think youth development is one thing few can argue Martinez doens't have a decent track record on, not just having the foresight to take a punt on Callum McManaman but others, too. Both McCarthy and McArthur were known to be decent but it was Martinez who turned them into Premier League players, now McCarthy is in the 5/10m bracket, apparently
I expect Ross Barkley to become a regular under Martinez, he'll get the freedom and confidence from Martinez to go out there and play his game, not constantly ignored by a manager who thought Phil Neville was a better midfielder