Manchester United have conceded 12 goals in six competitive games under Louis van Gaal, with Sunday's 5-3 humiliation against Leicester City revealing serious flaws in the team's defensive approach, which begs the obvious question of where it has gone wrong?
Lack of leadership
The summer departures of Nemanja Vidic, Rio Ferdinand and Patrice Evra saw United lose 1,096 games of top-level experience from their back four and, while nobody ever suggested it would be easy to overcome the loss of three such senior figures, the reality has been far worse than even the gloomiest predictions. All three had shown signs of age and wear-and-tear last season, but allowing each of the trio to leave now appears to have been reckless.
United's remaining defenders are young and lacking in experience. Tyler Blackett needs to be guided through games, but so do Chris Smalling, Phil Jones and Jonny Evans, who often relied on the presence of Vidic, Ferdinand and Evra to cajole them along.
So are United operating a three-man defence or have they now reverted to four at the back? Van Gaal continues to evade questions over his preferred system for United, so supporters are as confused as the players on the pitch.
Van Gaal, who has typically played 4-3-3 throughout his career, has spoken repeatedly about the need to the 'train the brains' of his United players, but for defenders schooled in 4-4-2, perhaps it is too mentally-taxing to impose a 3-5-2 system on them.
No defensive discipline
The secret of any back line, whether it be three or four defenders, is to maintain a straight line when pushing up.
United, however, appear to have been operating with a zig-zag approach when attempting to maintain a defensive line, with the second-half collapse at Leicester a direct consequence of the lack of defensive discipline among Van Gaal's defenders.
There is no organiser on the pitch and while injuries have not helped Van Gaal in this area. Had Evans, Jones, Smalling and Rafael been fit throughout pre-season, perhaps an understanding could have developed that would have avoided the problems exposed at Leicester.
But each of that quartet are often injured, so Van Gaal cannot rely on their fitness in the long-term.
Transfer market failings
Former Liverpool defender Jamie Carragher accused United of 'mismanagement' by failing to sign a top-class defender this summer, but almost £50m was invested in Luke Shaw and Marcos Rojo but little effort made to replace Ferdinand or Vidic .
Manchester City had a clear run to Porto's Eliaquim Mangala, who made such an impression on his debut against Chelsea on Sunday, while Dejan Lovren would also have improved United at the back, but no effort was made to rival Liverpool for the centre-half.
Van Gaal has complained of inheriting an 'imbalanced squad' from David Moyes, one with more number tens than central midfielders and a needless stockpile of wingers.
While that has been addressed during the transfer window, Van Gaal seems to have moved the problem around his team rather than solve it and it's no surprise that the defence is struggling with so many attackers in the team.
Only Daley Blind, a defensive midfielder, offers the back four any protection and he was overrun at Leicester, while the likes of Juan Mata, Ander Herrera, Angel di Maria and Radamel Falcao offer little or nothing in terms of defensive contributions .