The departure of experienced heads like Nemanja Vidic and Rio Ferdinand during the summer, and the failure to properly replace them, meant that question marks were raised about Manchester United's back line before the season had even started.
Louis van Gaal Playing 3-5-2 early on didn't help the cause, teams saw a clear weak link in the Old Trafford armour and exposed it. It was so obvious that when Arsene Wenger was asked before the game against Arsenal a few weeks ago what the game plan would be, he replied without hesitation that they would target United's defence.
Admittedly, they were playing youngsters Paddy Mcnair and Tyler Blacklett in defence, so targeting them is not exactly tactical genius. Though it does bring up the point that Van Gaal has not been helped by the astonishing number of injuries his squad has suffered.
They have been able to name the same back four for two consecutive games only once this season. Even now they have four regular starters out injured, with wingers Antonio Valencia and Ashley Young occupying the full back positions.
Despite all this, most of the United faithful do agree that even with the injury problems solved they still need to bring in some defensive reinforcements and highly rated Dortmund captain Mats Hummels fits the bill completely.
An integral part of Germany's World Cup side in Brazil during the summer and a constant performer at club level for the past few years, Hummels has all the traits one looks for in a modern day centre-back.
Dominant in the air, comfortable on the ball, possessing good pace and positional sense. The 25-year-old is also a leader, one United lacks in their defensive department. Every successful defensive unit has that one player that keeps the others in check and keeps everything calm, almost like a conductor directing an orchestra.
Vincent Kompany at Manchester City, John Terry at Chelsea and Sergio Ramos at Madrid all play that role - Hummels can be that man for Manchester United. The Bayern Munich academy graduate is at the peak of his career and would be a great addition to any side.
The problem for Van Gaal is prizing him away from Dortmund. Despite their horrible start to the season, Hummels is not one to abandon ship when the going gets tough and would likely want to at least end the season at the Westfalenstadion.
So a January transfer is probably not on the cards. Then again, it wont be easy come summer either, with Barcelona, Arsenal, Manchester City also reportedly interested and a bidding war a likely outcome.
One thing, though, is for sure: Manchester United need to go all out to try and buy Hummels, even if it means splashing the cash again, because he is what the team badly needs.