"He's a very good footballer," said O'Neill. "He's strong, he's at Manchester City where competition for places is strong.
"When he signed for City Mark Hughes said he was going to be signing an awful lot of players and true to his word they've arrived at the football club.
"I'm sure Gareth's fine and if you speak to him I'm sure he's pretty pleased with his decision.
"That's obviously something I can empathise with in many aspects because I was at a football club for 10 years myself as a player."
Asked what kind of reception Barry will receive from the claret and blue faithful, O'Neill replied: "You shouldn't be asking me that. I don't know."