It is an indisputable fact that Manchester United's defense is inadequate for their top four ambitions.
While youngster Patrick McNair had a solid debut to verify his inclusion in the squad, it was still a performance marked by juvenile uncertainty and naivety. These are issues Manchester United cannot have in their centre-backs when every game has to be won.
The problem for the likes of McNair, Tom Thorpe, and Michael Keane is that they do not have a leader they can look up to - someone who can help their development beyond the coaching staff.
And this is David Moyes' greatest mistake as the Manchester United manager.
Allowing Nemanja Vidic to leave the club - a solid, experienced centre-back - has been the most significant component of Manchester United's defensive demise.
The failure to sign a commanding centre-back would have been irrelevant had Vidic been kept at the club. If Moyes could keep Wayne Rooney, why not keep Vidic?
The Serbian was the epitome of steel in the United defence. He was always in the right position to make clearances from threatening through balls, and to thwart away dangerous crosses with powerful headers.
But he was also a composed, calming influence on the back four. He played simple, and kept the ball moving, never trying to do too much. It was an issue that Marcos Rojo and McNair both had against West Ham, occasionally trying to go long instead of playing a simple ball to the full-backs, or finding the feet of Daley Blind and Ander Herrera.
Although the United defence was solid, they had the full support of Old Trafford chanting them on. The hostile atmospheres away from home are when a leader, like Vidic, is absolutely crucial to keeping the team calm and seeing out victories.
It was most evident against Leicester City, when four second half goals changed the game from a feel good Man Utd victory, to a shocking, humbling defeat. Vidic would have never let such a collapse occur - the crowd would have remained quiet.
Experience is key
While the failure to sign an outstanding centre-back was clearly the disappointment of the transfer window, the problems began much earlier with the failure to keep Vidic.
Manchester United lost much more than a defender. They lost an experienced player, a ruthless competitor, a calming influence, and - most importantly - a leader.
Louis Van Gaal's priorities must now be centered around replacing Vidic. Otherwise, the defensive woes could make the top four an impossible ambition.