I guess that for a start, it'll be a bit like Henderson leaving Sunderland. Henderson got booed on his return to Sunderland in his first season IIRC, but I think the reception has improved since then, and he remains a Sunderland fan. I suppose it's a matter of fans needing time to accept that the departure was inevitable and that the player's decision to leave was a reasonable one - as long as the parting was amicable.