Roy Keane allegedly headbutted by fan after Arsenal win against Man Utd as Micah Richards intervenes to defend fellow Sky Sports punditChris BurtonGetty/TwitterManchester UnitedArsenalPremier LeagueArsenal vs Manchester UnitedManchester United legend Roy Keane was allegedly headbutted by a fan during the Red Devils’ defeat at Arsenal, with Micah Richards joining the tussle.Article continues belowArticle continues belowArticle continues belowArticle continues belowRed Devils legend at Emirates StadiumConfronted by supporter in north LondonSecurity staff forced to step in