Middlesbrough boss Neil Warnock says he felt "embarrassed" by the decision to award Swansea City a match-winning penalty at Stoke City in midweek.
"Michael O'Neill did ever so well not getting fined," said Warnock.
The former Cardiff City boss added: "I don't know what to say without getting into trouble really."
After seeing his side lose to the late penalty, O'Neill said: "It is a big call, an incorrect call in my opinion having seen the incident back.
"I think the contact was the Swansea player on his own leg. I think he inadvertently tripped himself up.