Normally, the offside line is drawn in relation to the last but one player behind (usually the last defender before the keeper in normal circumstances). However, when the keeper rushes off his line ahead of a defender as seen below, the goalkeeper becomes the last but one player and becomes the point where the offside line is drawn. Therefore, as seen above, every Nigerian player behind ONDOA is offside.
The Cameroon defender on the line is then considered as the goalkeeper and the goal is cancelled because the Nigerian players who are offside are blocking the view of the Cameroon player on the line.
