"We have never had a run like this - conceding 11 goals in four games. We are scoring a lot of goals but we have to try and improve in defence," said the keeper.
"Scoring goals is the most difficult thing in football but now we must sort some of the problems we're having in defence.
"We've always had the balance between attack and defence. That's why we're always there in the Champions League and cup competitions, because we are a team with balance. We have to get back to this way."