Footage from inside the Emirates Stadium emerged shortly after the Gunners’ 3-1 victory showing Keane’s Sky Sports colleague Micah Richards pinning a supporter against a wall during an angry confrontation.
Both pundits are believed to have left the main television studio at the top of the West Stand as the match was reaching its conclusion and were making their way pitch-side for their post-match analysis.
They were waiting for a lift at the members-only Highbury Bar when Alejandro Garnacho thought he had scored for United to snatch all three points, though the effort was ruled out by VAR for offside.
Richards and Keane were about to return to the Sky Sports studio to watch replays when the incident occurred, with the Daily Mail reporting that a headbutt was aimed at the Irishman which struck him on the chest and chin.
A widely circulated video clip appeared on social media and showed the immediate aftermath, with Richards grappling with the alleged attacker and pushing and holding him back while a furious Keane stood just behind him.
The pundits called for security but had to leave in order to get pitch-side before the end of the game and the fan fled the scene in a crowd.
Police, with the help of Arsenal, have been combing through CCTV footage to try and identify the supporter and have now arrested a 42-year-old man.
A statement from the Metropolitan Police on Monday afternoon said: ‘Police are investigating an incident at Emirates Stadium on Sunday, 3 September, during which a man was assaulted.
‘On Monday, 4 September, a 42-year-old man was arrested on suspicion of assault (ABH). The man has been taken into police custody. Enquiries are ongoing.’
Neither Richards or Keane have spoken about the incident yet nor did they let on that anything had happened when they provided their post-match analysis after the game.
According to The Sun, both were ‘left shaken’ by the altercation and Sky Sports intend to beef up their security moving forward.
Match of the Day host Gary Lineker, who records a podcast with Richards, provided an update of sorts on his colleague’s well-being, taking to social media platform X, formerly know as Twitter, to say that the former Manchester City defender was ‘all in one piece’.
For more stories like this, check our sport page.