The 39-year-old goalkeeper had been starting for his country while he was number one at Aston Villa late last season but with his move to the Britannia Stadium where he is expected to be number two behind the promising Jack Butland, hiss spot in O'Neill's side for upcoming Euro2016 qualifiers is under threat.
"You'll have to ask Shay. He's obviously not going to start in the side. Like anyone else, I think coming into the games in September, you'd like as many players as possible to be playing regular first team football."
Ireland, who sit fourth in Group D qualifying for next season's Euros in France, meet Gibraltar in Portugal on September 4 before taking on Georgia in Dublin three days later.