The Reds have conceded three goals in each of their five friendly games, including a 3-3 draw against Valerenga in Oslo on Monday night.
Agger, who scored two of Liverpool‘s goals in Norway, says the rate of goals leaked by the Reds can’t be accepted as the side look ahead to the opening game of the season, at home to Sunderland, on August 13th.
“On Monday it just wasn’t good enough, especially in the first half,” he said. “The second was OK but it still wasn’t what it needs to be. The amount of goals we’ve conceded is not good enough. We need to show we can keep a clean sheet and must defend better.
“If you are a footballer, you have to be a perfectionist and so far we have to admit it’s not been good enough. Kenny has his way of getting his point across and has said himself that we need to be streetwise – that’s what we have got to do.
“We have a lot of work ahead of us – we cannot afford to concede so many goals,” he said. “We have some new signings and are still working them into our system but to let in three is not our identity. We must be optimistic but we were far behind United last year and need to improve.”