I have said this before much earlier in the thread, but that point about loads of managers not trusting him doesn't hold that much water under examination if you look at the circumstances of those clubs when he was there.
Barcelona - had Messi and Neymar ahead of him, then when he went back after his loans Suarez was there as well
Everton (loan) - was one of our best players during his loan spell, only that injury set him (and us) back
Sevilla - started well but didn't fit into Emery's very successful system. Made no sense to accommodate him to that system given that he was on loan anyway.
Everton (permanent deal) - by the time he came back Martinez had convinced himself into playing a patient / bollocks style that didn't suit him (or us for that matter), used him sparingly and played worse players in his position like Lennon and even Cleverley and Osman on occasion. Koeman has picked him on the odd occasion but then dropped him afterwards, usually because other players screwed up (Watford away, or Leicester at home for instance).
What he needs is a run in the team; however gives him this will benefit from it. I just hope its us because we will look very stupid indeed if we let him go.