Charlton Fight Sankofa Red Card
The 21-year-old defender was sent off for a tug on Gunners' striker Robin van Persie in the 29th minute at The Emirates.
Charlton Manager Alan Pardew claims Talal El Karkouri was the last man and that Van Persie was in an offside position.
Pardew said: 'The decision against us was a triple whammy. He should have been given offside, two yards offside by the way.'
Pardew added: 'Secondly, he didn't pull him back too hard and the player went down quite dramatically; and then Osei getting sent off as well, that was a big blow for the team.'
Should Sankofa lose the appeal then The Reds will be without a right back for the Forrest game in the FA Cup on Saturday. Luke Young is still sidelined with injury.