Violent scenes at the end of the Manchester derby cast a shadow over a remarkable encounter that saw United secure a late 3-2 win.
Rio Ferdinand was struck by a missile and was then confronted by a fan on the pitch - an incident which appeared to be defused by Manchester City goalkeeper Joe Hart.
The fan was subsequently led away from the pitch by police.
Ferdinand was seen showing an object to referee Martin Atkinson at the end of the match.
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