Rio Ferdinand laughed off the incident that saw him struck in the face by a coin as he celebrated Manchester United's winning goal in their 3-2 success at Manchester City on Sunday.
The English centre-back was left with blood pouring from his face after being hit by an object apparently thrown from the crowd in the aftermath of Robin van Persie's injury-time winner for United.
Writing on Twitter, he said: "what a result,3points! Sweet! Whoever threw that coin,what a shot! Can't believe it was a copper 2p....could have at least been a £1 coin!"
A City spokeswoman said the club were reviewing CCTV footage of the incident with police and that they would pursue the matter "vigorously".
City manager Roberto Mancini claimed not to have witnessed the incident, but he condemned it nonetheless.
"I didn't see, so I don't know what happened," said the Italian.
"We have fantastic support but we can't do what that person did, because it's not good."
A fan wearing City colours also had to be restrained by home goalkeeper Joe Hart after walking onto the pitch and making his way towards Ferdinand after the incident.
City had not lost a home game in the Premier League for two years and their defeat saw United establish a six-point lead at the top of the table.