Sunderland boss Roy Keane is confident his defence are learning from their mistakes so far this season.
Sunderland have not kept a clean sheet since the opening day victory over Tottenham, and as they currently average only a goal a game themselves in the league, that is proving a problem.
Asked how that lesson will be learnt, Keane said: "From games, from the lads gaining experience, from being punished for your mistakes.
"That is sometimes the hardest way to learn, and in the Premier League, it is certainly that.
"It just comes from games and the experience of playing at the top level against the top strikers."