The South Korea forward is wanted by Germany's Augsberg.
O'Neill told the Sunday Sun: "Ji has had a tough old time since the Olympics, and he wants to play some regular football. If he's going to be given that opportunity to play regularly [at Augsberg] then it is something I would look at.
"But if he would only be used intermittently, we might as well keep him here. We'll see. There are a couple of clubs interested and I need to speak to them first."