The ex-Leicester City boss left his post at Parkhead because of the failing health of his wife, but now it is believed that his wife is recovering well and he could be coming back to the game very soon.
Although O'Neill has been linked with other clubs, but it is believed he would revel in the opportunity to manage Newcastle United.
Should the worst come to the worst, Shepherd is even considering a short-term choice, possibly Alan Shearer as player-manager, until O'Neill becomes available.