Nathan Thompson has confirmed he was not booked in the incident which left Karl Robinson fuming.
The new Oxford United boss was raging with the Pompey man, after he was slapped by Alex Mowatt following his second-half penalty miss in his side’s 3-0 loss.
Thompson faced up to the U’s midfielder as temperatures rose, prompting a reaction which saw Mowatt dismissed.
Robinson insisted referee Charles Breakspear told his players the former Swindon captain was also booked in the incident.
That would have meant the 27-year-old should’ve been dismissed after picking up a first-half caution.
Thompson confirmed to The News after the game he’d not picked up a caution, however.
Robinson, though, pulled no punches with his take on the key moment.
He told Sky Sports: ‘The referee has made one of the biggest mistakes I’ve seen for a long time. Thompson was booked in the first half and what he did was a disgrace. An absolute disgrace.
‘My player will be reprimanded, but what he did to my player, to not get booked for it and then do what he did. You’ve all seen it and professional footballers should do what they did.
‘And then the referee tells my players he’d booked Thompson. It’s not until my players came in and they said he’d been booked before half-time.
‘I’m a little bit confused. Did the referee say that to diffuse the situation? Has he told them that, made a mistake and booked the wrong person?
‘You can’t do what he’s done. He told my captain he’d booked him.’
Despite the scoreline, Robinson was adamant his team were the superior outfit.
He added: ‘We were the better team by a long way.
‘We knew they were suspect to the counter-attack and that was the case.
‘Everyone in the stadium would say Oxford are a very good side.’