From the start of the season it was obvious Louis Van Gaal’s squad was unbalanced, with a high proportion of world class attacking talent contrasting with promising but inexperienced defenders, yet to reach their peak. This imbalance has been clear throughout the season, with United’s attack scoring a respectable 16 goals. However the defence has conceded 14 in 10 games (and that is with some fabulous performances from David De Gea), only keeping clean sheets against relegation candidates Burnley and QPR.

There are several reasons for this, but one major one is Van Gaal’s change in defensive approach from David Moyes last season. Moyes instructed his team to sit deep in two banks of four, forcing the opposition to play in front of United. By contrast Van Gaal has ordered United to push up the pitch with a higher defensive line. With a high defensive line it is vital that there is pressing in midfield, so the ball can’t be played in behind easily. United haven’t pressed as high up the pitch or as intensely as, say, a Guardiola or Bielsa team, but they have been a lot more pro-active in winning the ball back than last season.

The problem with pressing and pushing higher up the pitch is it can be hard to prove statistically, with no one stat as evidence a team is doing it. However a picture can be made from several different stats.

For example if a team consistently sits deep, it makes sense they will have to do more penalty box defending, therefore make more clearences and blocks. Under Moyes United made 37.2 clearances per game and 3.1 blocked shots. Under Van Gaal both stats have decreased, with clearances down to 28.6 and blocks to 2.8.

If a team is pressing, it makes sense they will attempt more tackles. Pressing also leads to more fouls, as more cynical tactical fouls occur to prevent opponents breaking into space behind. Under Van Gaal attempted tackles have gone up from 25.5 per game to 26.7, and fouls have increased from 10.6 per game to 12.1.

It makes sense that if a team is pushing high up the pitch they will concede less shots, with the opponent spending less time close to their goal. Under Van Gaal United are conceding 10.6 shots per game, 11% less than the 11.9 under Moyes.

The more salient fact is where these shots are being conceded from. If a team sits deep they may concede more shots, but the majority will be from outside the box. This season Chelsea are a good example of a team that generally defends deep with men behind the ball. They have conceded 53% of their shots from outside the box, 43% inside and 4% inside the six yard line. By contrast United have conceded only 37% of their shots from outside the box, with 54% coming from inside and 9% inside the six yard line.

This illustrates the risk with playing high up the pitch. While you push away the opponent from goal and concede less pressure and chances, when they do get in behind, the chances are more dangerous.

None of these stats individually prove much, but taken together it is clear that United are playing higher up the pitch and are more pro-active without the ball than under Moyes. However, having established United’s poor defensive record, does this mean Van Gaal is taking the wrong approach? In a word, no. The problem is not the approach itself, but rather the execution. For a team with a similar approach, but carrying it out more effectively, we only need to look at the Premier Leagues current overachievers- Southampton.

This Southampton side learnt to press under Mauricio Pochettino, and while they aren’t doing so quite as high under Ronald Koeman, their defensive approach is based on a high defensive line (they have the least clearances in the division with 20.1 per game) and midfield pressing (they have the most attempted tackles in the league with 32.7 per game), very similar to the approach Van Gaal is attempting.

However Southampton have had a lot more success, conceding only 5 goals (9 less than United), have conceded the least shots on target in the league (24) and kept 6 clean sheets to United’s 2.

If both are attempting the same defensive approach, but United’s players are probably individually better, why such a vast gap in results? The key is cohesion. Pressing as a unit requires hours of training ground work and an intimate knowledge of your teammates. Equally keeping a high line means the back four have to have a keen understanding of when to push up, when to drop off, and must make all movements together.

To develop this cohesion, the team must play together consistently. 8 of Southampton’s players have played together in all 10 premier league fixtures so far, compared with United’s one. They have played the same centre back partnership 6 times (Fonte and Alderweireld), the other pairing 4 times (Fonte and Yoshida). Having reverted from a three man defence to a four, injuries have meant United are yet to play any centre back pairing more than twice. Whereas Sothampton are used to pressing as a team under Pochetino, it is new to the majority of United’s squad.

A lot of people are calling for United to sign established, top class defenders. No doubt this would help, but the players Van Gaal has suit this system. They are young and fast, modern defenders suited to a high line. With top quality defenders costing more and more, what Van Gaal really needs is to get his defenders fit, and playing together to develop cohesion.

Similarly in midfield all the tools are there- Di Maria, Herrera and Blind are all energetic, intelligent pressers. What they need is time together in a consistent formation (probably a diamond), to press efficiently as a unit.

Playing a high defensive line can be a risky strategy, and United have often conceded purely because opponents have got in behind (Berahinho vs West Brom, Vardy vs Leicester). But United only need to look to Southampton to prove that, with more consistency of selection and cohesion throughout the team, Van Gaal’s defensive methods will be very effective.