The FA has confirmed that it is investigating an incident involving Rio Ferdinand in Sunday's Manchester derby at the Etihad Stadium.
Ferdinand sustained a cut to his eye after an object was thrown at him during Manchester United's 3-2 victory over Manchester City.
A supporter also came onto the pitch to confront Ferdinand, but the individual was restrained by goalkeeper Joe Hart.
Premier League champions City have since offered their apologies to the defender following the incidents.
"It is disappointing that after a great game and advert for the Premier League that we are discussing this issue," said an FA spokesperson.
"We will work with the clubs and authorities to identify those responsible and support the strongest sanctions available, including life bans.
"We condemn any such acts and it is simply unacceptable that any player is exposed to injury in this way. To witness Rio Ferdinand leaving the field with a cut above his eye to receive treatment is appalling."
Police arrested another man for alleged racist chanting on what was a controversial afternoon at the Etihad Stadium.
