If Boxall wasn't prepared to wait patiently until his time come, the other option is to get better at your craft. Become a better option than the incumbent. Radical idea I know
I think he may have been close to this. He was certainly close to first choice at fullback.
That is true. I would rate Boxall equal to or better than Manny, as per their form midway through last season.
But both Siggy and Dura played very well at that time and Boxall was not getting enough game time as CB. If I am not mistaken, he was headhunted for a CB position in Brockie's new team in SA. So it panned out as planned: he is hopefully getting better at his craft by playing regularly (although not in a better level competition IMHO), and is earning money to afford a house in Auckland once he's back.