Dan Agger cannot explain why Liverpool's defending has been so poor this season.
Liverpool's leaky defence has been blamed for the club's worst run of form for 22 years, with six defeats already this term and 17 goals conceded in their first 13 matches.
Agger said: "We must defend as a unit, it is not just about four men at the back. Conceding goals like we are is just not good enough.
"We are normally so strong and we don't concede goals like that. What is wrong? To be honest I haven't got a clue. I feel okay, but I am not 100% fit after my back problem. I need match fitness, but that will return slowly."
He added: "Defeats do affect the team, but everyone just has to carry on, work hard, and things will be okay.
"We need to learn to play consistently through a game, that's simple really.
"We were at home against Lyon in the Champions League on Tuesday, we should have been able to finish the game off a long time before they scored. We were leading and missed good chances that could have wrapped things up.
"In the end it showed that we were not good enough. We have to address that. It is Manchester United next, so we have to raise ourselves for that. It is all about hard work. If you are not playing well that is the way to improve. Everyone must be focused now."