I've read the report again and think the sentence is okay - he has previous for common assault and possession of drugs going back four years or more when he would have been tried as a juvenile and this time he was found guilty of actual bodily harm, not the more serious grievous bodily harm.
The previous conviction for common assault could have been anything relatively minor such as a push or a threat.
The five-year football banning order and the £3k compensation for the victim will have more effect on him than a short stint in prison.
We do need more prisons, though.