United have had a poor start to the season under new boss Louis van Gaal, losing to Swansea City and drawing with Sunderland after another frustrating summer in the transfer market. Whilst the likes of Mats Hummels, Arturo Vidal and Juan Cuadrado have been linked with moves to Old Trafford, the Red Devils have so far only landed Luke Shaw, Ander Herrera, Marcos Rojo and Angel di Maria - when much, much more was needed to turn the club around following a seventh place finish last season.
The latest blow was missing out on Roma defender Mehdi Benatia, with the Moroccan joining Bayern Munich despite reported interest from United. The club's defensive frailties were once again highlighted with the shock 4-0 defeat to MK Dons in the Capital One Cup on Tuesday night, and a new signing is needed to try and replace Nemanja Vidic and Rio Ferdinand in the heart of the United backline. Here are five alternatives for United to consider with the transfer deadline approaching this Monday.
Holger Badstuber, Bayern Munich
With Benatia arriving at the Allianz Arena, Badstuber could find it hard to start regularly this season having missed most of last term through injury. Van Gaal was the man that brought Badstuber into the Bayern first team back in 2007, and is credited with being the manager to have helped develop the German international. A loan deal could be beneficial for all parties in order for Badstuber to get back to his best.
Dante, Bayern Munich
If Bayern don't want to let Badstuber leave, Dante could become available instead. The Brazilian was strongly linked with a move to Old Trafford in January, and would be the top class signing that United need in order to improve their defence with some experience.
Philippe Mexes, AC Milan
There were some tentative links suggesting that Mexes could be a target for van Gaal having slipped behind the likes of Adil Rami, Alex and Cristian Zapata at the San Siro. The 32-year-old is far from a long term option for United, but he's strong and confident in possession so could be used as a stop gap before making a big run at signings Mats Hummels either in January or next summer.
Jan Vertonghen, Tottenham Hotspur
This is almost certainly the most unlikely target, but lining up Vertonghen would be a big sign of ambition given his displays for Tottenham. Spurs landed Federico Fazio today which could at least ease their stance on the Belgian, who has all the attributes to play in van Gaal's defence.
Ron Vlaar, Aston Villa
There have been murmurings on Twitter that United could be interest in Vlaar, who starred under van Gaal for the Netherlands at the World Cup. The Aston Villa man has bags of experience at 29, and would again offer a short-term solution - and familiarity with van Gaal's system.
Who should United target to improve their defence?