Celtic boss Brendan Rodgers will be keen to add some extra depth to his squad in what is expected to be a busy transfer period this summer. Firstly, the goalkeeping position is an area that needs to be addressed amid Joe Hart’s impending retirement. Potential replacements have already started to surface in media circles, including RC Waalwijk stopper Ettiene Vaessen, Trabzonspor’s Ugurcan Cakir and Liverpool number two Caoimhin Kelleher. Former England international Hart has been a leading presence on the pitch and in the dressing room, making the task of finding a suitable alternative a cruci…