Erik ten Hag admits he is at a loss to explain Manchester United's poor defensive performances.
The Red Devils have conceded 14 goals in their last five games and 10 in the last three, with three goals against Bayern Munich in the Champions League on Wednesday not enough even to earn them a point.
United boss Ten Hag said: "We have shown that we can do it because last year we had the most clean sheets in the Premier League because of the team, because we defended very good as a team, so we have to get back to that standard.
"Of course I am pushing the team and demanding from the team, and from the start of the season, but they are human beings, not robots, so, why they are not doing it, I try to find out and I try to give the solutions and try to motivate the players to do the job.
"When you are in a period like we are in always as a manager you are asking yourself these questions. My job is to get them to do the job."
On United's tendency to concede goals soon after a restart, Ten Hag added: "(We're) not concerned but we are aware of it. Of course you can't close your eyes for things like this so we coach the players, we coach the team in that fact."
Question marks have been raised about the attitude of United's squad, with clips from the Bayern game apparently showing players not chasing back as hard as they might.
Ten Hag does not believe a lack of willingness was to blame, though, saying: "It's always a concern when we didn't run but I think against Bayern it was not the case.
"In certain situations yes so it's also to recognise in which situation is it about they didn't recognise it and didn't make the right decisions or is it about willingness?
"Against Spurs, we didn't run too much. But I think against Bayern we did our best from physical outputs but we didn't always run in the right moment.
"If we bounced back like we did in Munich, you can't say the spirit isn't right. I think we have other problems than that."
Australian Associated Press