Mustapha is a bit of a utility forward from what I've seen of him, he's been on loan last season already. Was seen as a prop but seems to lack the physique, if not the toughness. I can see him as a loose forward and occasionally filling in at prop. Corey Johnson is a hooker and seems highly rated by some but he's been in and out of the game a bit. A crafty sort of dummy half rather than a runner apparently. Could be a better option than Flanagan. I'm told O'Connor is a loose forward.
As has been said elsewhere if Leeds get some injuries up front we might not have these lads for long.