Manchester United are currently enjoying a winning streak of four games, including one vital victory against Premier League rivals Arsenal. With this good form and £150 million, Louis van Gaal has put his team in the top four.
That said, despite the Red Devils' good form they have looked undeniably vulnerable at the back. This is largely due to the the injury overload in defence with Jonny Evans, Phil Jones, Marcos Rojo, Daley Blind, Michael Carrick, Rafael, Luke Shaw, Paddy McNair and Antonio Valencia all having significant spells on the sideline.
Furthermore, both Tyler Blackett and Chris Smalling have received red cards and suspensions.
Although they have had a number of central defensive injuries and suspensions, ultimately the reason for their defensive frailties is their injuries at full-back.
Undoubtedly, United would be a lot stronger if Evans, Rojo and Jones had been fit however formation, structure and shape is fundamental in modern football.
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One of Manchester United's most gaping holes is their depth in full-back with just Rafael and Shaw as recognised, natural full-backs. Consequently, when both full-backs are injured, United lose their shape.
Van Gaal has done brialliantly to grind out results and has shown his tactical versatility given his shortage of defensive options. With Shaw and Rafael out Van Gaal has shifted his formation to a narrow diamond with Young and Valencia providing width and both doing good jobs there.
However, the shape of the team is unbalanced, this is due to Young and Valencia getting forward in support and leaving just Carrick to screen the defence. As a result, United are often outnumbered at the back and susceptible to the counter attack as seen clearly against Stoke City, Arsenal and even at times Crystal Palace.
Change of tactics
In contrast, Chelsea and Southampton have conceded just 11 and ten goals respectively. This largely due to their solid structure. With two midfielders sitting in front of the back four in Nemanja Matic and Cesc Fabregas or Morgan Schneiderlin and Victor Wanyama, this gives defensive cover, thus giving license to the full-backs to go forward.
However, this is different to United as they don't rely on full-backs for width. Chelsea use Eden Hazard and Willian out wide with Branislav Ivanovic and Cesar Azpilicueta supporting meaning they are threat going forward but also strong at the back.
Therefore, their summer signing Fabregas can go further forward at times as they have the option to leave a full-back to defend with a holding midfielder assisting the defence.
As a result, due to their solid formations Chelsea and Southampton are defensively very strong whilst productive going forward and this formation with their quality is the key to their success.
Therefore, although Van Gaal has done well to shift formations to tailor to the clear deficiencies in the United squad, the reason for the defensive vulnerabilities is largely down to their unbalanced formation and their reliance on makeshift full-backs Young and Valencia for width.
For more consistency, Van Gaal must invest in more cover in the full-back position. However when Shaw and Rafael are fit, United will look a lot stronger at the back as they should have the structure more similar to that of Chelsea, which offers a more balanced shape which with the quality United have will undoubtedly lead to success.