David Moyes, speaking to the Telegraph, has accepted that the Red Devils do not have the "five or six world-class players," needed to win the Champions League.

The Scot is understood to have the funds available to attempt to strengthen United's ageing squad in January. Having identified Leighton Baines at Everton, Athletic Bilbao midfielder Ander Herrera, and France defender Eliaquim Mangala at FC  Porto, Moyes may feel that he can pull off the required signings.

However, acquiring 'world-class' players in the winter window may prove to be very difficult. Mark Ogden, writing in the Telegraph argues that, 'moving for all three players in January may present new problems and United are wary of entering the mid-season transfer window because of inflated valuations and some targets being cup-tied in Europe.'

Ogden's point could prove a crucial one. A number of managers in the past have realised just how difficult it can be to sign players in the January window. Even the mighty Manchester City discovered this when their only signing in January 2012 was 32-year-old midfielder David Pizarro, on loan from Roma.

Roberto Mancini, the manager of City at the time, had previously identified a number of targets but efforts to sign other players proved unsuccessful.

United could be frustrated for a number of reasons. Firstly, in many cases, as January is the midpoint in the season, a particular player may have become crucial to their current club's performance. A perfect example would be Everton's Baines. There are no players at Everton that could fill the void left by Baines. Consequently, if Moyes did manage to acquire him, it would be at a massively inflated price.

A second issue identified by Ogden is that players from clubs that are in the Champions League will become cup-tied if they appear in the European competition at any point before they move to their new club.

If Moyes is really targeting 'world class' replacements, then the chances are that the players needed will be cup-tied. A cup-tied player will not be able to add anything to United's European campaign.

A third issue that must be considered is around the stability of the present squad. Dressing rooms can places of fragile relationships and constant tension. If a clutch of new signings do not get on with the rest of the squad, performances will inevitably dip.

A club that nearly came a cropper in this way was Newcastle last season. Having acquired a large French contingent in January, there were issues around squad cohesion and understanding.

Moyes will need to consider all of these issues if he is to strengthen United's squad in January. It may be absolutely crucial because if the current squad limps on till the end of the season, United may find themselves sitting outside of the top four for the first time in a long time.

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