Manchester United have been an impressive force up front this season with the addition of Robin Van Persie in the Summer appearing to pay-off for the Red Devils.

However, one issue that United seem to face season after season is defensively. With Rio Ferdinand looking slightly below par and Johnny Evans error prone, United's central defence appears to be leaking.

One noticiable absentee is Vidic - one of the best defenders in the world. The Serbian has struggled with injury in recent seasons and has missed almost all of this season.

With the news that the defender could miss at least the next month, this could greatly effect United's chances of a league title or european trophy.

In the 2011/12 Champions League Sir Alex opted to rest a lot of players including defenders with Chris Smalling and Phil Jones used as they crashed out at the group stage - in embarassing fashion. 

With Jones and Smalling both injured along with Vidic, United have been resigned to having Michael Carrick as a back-up defender.

With a busy November period coming up United's defence will need to be as solid as possible and the loss of Vidic for a sustained period could lead to more points dropped than usual.

We have seen this season defensive errors cost United with the core being the most vulnerable - Michael Kightly's goal for Stoke at Old Trafford, also Gareth Bale's display the lack of pace and general exposed nature of the Red's centre-back position. 

Manchester United have conceded fourteen goals in nine games - five more than Chelsea and Manchester City - arguably their biggest threats this season. 

Whilst United will always be able to out-score teams on their day, on an off-day, their defence may well cost them dearly.