He has spoken repeatedly to him about his disciplinary problems, and while he continues to admire him as a player, he knows the former Middlesbrough man has to clean up his act.
O'Neill said: "We don't have a conversation every single day about it, but we talked at the time he was out.
"Obviously he was disappointed, but not half as disappointed as we were to know that he was missing from the games and through his own fault.
"Now if it had been something that we had been able to have looked at, and thought there were mitigating circumstances or something like that, then perhaps it might have been a different issue, but no.
"And yet the previous time he was sent off he was booked in the first couple of minutes of the game against Newcastle, but had a great game all together and was able to show that discipline, which was very, very important, particularly in that game.
"Then to come off at the end of the game and find out when I arrived in the dressing room that he had survived all of that and got himself sent off for speaking to the referee..."