The Manchester City player's sickening challenge left Mendes on a hospital drip.
Mendes spoke exclusively to The News to say he was feeling okay the day after he had been left out cold by the sickening forearm-led challenge.
Mendes said: 'I feel okay. I'm feeling better now. I feel relieved.
'I don't remember anything about the incident. I can remember the first half and bits of the second half but nothing more.
'The next thing I remember is bits in the ambulance. I haven't seen a video of the incident so I don't really know what happened.'
Manchester City issued a statement in which Thatcher apologised for the foul, but that has not stopped demands from fans calling for him to get a lengthy ban from the game.
And the FA have now revealed they are exploring whether Thatcher could be punished.
Referee Dermot Gallagher's decision to show Thatcher a yellow card meant the FA would not normally get involved under FIFA guidelines.
But because this was such an exceptional case, the FA's compliance department will now meet within the next two days to analyse the incident, taking into account video evidence and the referee's report.
Thatcher also faces a police investigation following his horror assault.
Greater Manchester police have confirmed they are following up a number of complaints from supporters.
Thatcher's attack left Mendes unconscious and in hospital.
A statement from Greater Manchester police said: 'We have received a number of complaints from the public following an incident which left a player injured in the Manchester City versus Portsmouth game.
'Officers will now be liaising with the injured player, clubs and the Football Association to review this matter and determine if any further action is required.'
FA spokesman Andrin Cooper said: 'We're looking at whether this may possibly be an exceptional case and are looking at what options may be available under our disciplinary regulations.'
Blues boss Harry Redknapp said: 'It was an horrendous challenge. We all know how bad it was. How was that not a red card? What is a red card if that's not?'