Old fullbacks are rarely a good idea, especially given the demands of the modern game. I wouldn't touch Zabaleta now, however good he was in his prime.
Right back is an interesting spot for us this summer because we need better than Holgate/Kenny but without making a significant investment. I have this horrible, unshakable feeling that we're going to add Cuco Martina, which would be a low-key disaster. He'd be cheap, but Martina is hardly better than the aforementioned players and he's as good as he's going to get. Kenny and Holgate, on the other hand, will improve with game time. It's probably just paranoid speculation on my part but I see this guy linked with us once a month and it drives me crazy. We should be doing better than signing dross from the manager's previous club.
Hopefully Walsh finds someone better because we'll need the extra quality there.