When Sir Alex Ferguson goes to bed each night one can only imagine what his greatest concern is as he tosses and turns between the sheets, with Manchester United’s defence being as porous as it has been for many years.

The likes of Demba Ba and Papiss Cisse will smell blood as United are face Newcastle in the Premier League on Sunday; and Ferguson needs to find the solution soon if his side are to challenge on all fronts again.

United go into the match on the back of another victory at CFR Cluj; but the game did not run as smoothly as it should have done, with Sir Alex Ferguson’s side falling behind to a goal by Pantelis Kapetanos that saw the defence torn apart with just one pass.

Johnny Evans and Patrice Evra lost the markers and left the Greek striker with far too much space to give the Romanians a shock lead after 14 minutes.

Unfortunately this has become a regular occurrence for a side who were once renowned for their defensive solidity, especially when the partnership of Rio Ferdinand and Nemanja Vidic was at the peak of its powers.

The statistics make for alarming reading for United fans; the Reds have fallen behind in six of their nine matches this season, losing two, as well as conceding 11 goals in those games.

But there is sound reasoning behind these defensive lapses, as United seem to be continuously blighted by a series of injuries at the back.

Phil Jones and Chris Smalling have missed all of the matches so far, suffering knee and metatarsal injuries respectively, while Vidic is set to be out of action for at least a month longer after suffering another knee injury.

The situation is far from ideal, but it should not be used as an excuse for United’s defensive fallibilities, especially with the calibre of players at their disposal who are as equally capable of doing the job well.

Despite being frozen out of the England squad, Rio Ferdinand is more than experienced enough to marshal the defensive effectively and has the ability to play the ball out from the back.

Johnny Evans also rose to the occasion in the long-term absence of Vidic last season and matured into a centre-back of Premier League quality.

But what has become clearly evident is that the Reds have struggled to deal with pace this season, as seen when Gareth Bale waltzed past Ferdinand to score Tottenham’s second goal in their 3-2 victory at Old Trafford last week.

The likes of Rafael and Patrice Evra may possess pace of their own when going forward, but their worrying inability to track back and defend is becoming a growing concern.

This is particularly the case with Evra, who not so long ago was being compared with Ashley Cole as the best defender in the Premier League, but sadly he appears to be undergoing a large dip in form.

The arrival of Alexander Buttner has kept the Frenchman on his toes, but despite his promise, the 23-year-old’s sometimes over-willingness to attack would be exposed by the best teams.

Additionally, the goalkeeping situation at Old Trafford has hardly helped matters, with Ferguson switching between David de Gea and Anders Lindegaard. Lindegaard is seemingly preferred for league matches; whereas De Gea has been selected to play in European and cup matches.

The lack of a consistent number one surely does not help matters, with defenders needing to grow used to playing in front of a certain goalkeeper.

The last time Sir Alex rotated as much with his goalkeepers came in the disappointing period between 2003 and 2005, where neither Tim Howard nor Roy Carroll could nail down the first-choice berth.

In order to address these concerns and become more solid at the back, the United defence must improve their organisation and work better together as a defensive four.

The likes of Rafael and Evra are great when going forward, but must recognise the need to track back at the slightest hint of danger; while Ferdinand as the most experienced centre-back, must take charge of the defence and allow Evans to follow his lead when the side are under attack.

There is no doubt that the team has more than enough quality to turn the situation around, with organisation being the key issue here.

As soon as the likes of Vidic, Smalling and Jones return, United will be in a much healthier position to consign these defensive concerns to history and allow Ferguson to sleep well once again.