I guess that depends on a couple of things. If you believe Robinson, he is going to rely more on youngsters next season, so plan B may be the reserve team right back.
Or he may be signing (or already have signed on pre-contract) a new right back.
Or we might just go with a back 3 combo of any three from Carroll, Gallagher, Dunne, Maguire, Mugabi, and, if the rumours are true, Lamie.