Arsenal vs Manchester United: Five things that we learnt from the Emirates

(Getty Images)

1. Louis van Gaal isn’t afraid to complicate things

It was seemingly not enough for Manchester United to deal with a remarkably extensive injury list - added to 16 minutes in here with Luke Shaw limping off to be replaced by Ashley Young - so manager Louis van Gaal decided to revert to a back three in defence.

It is a system United’s players are palpably uncomfortable with - hence why the Dutchman abandoned the formation not long after the season started - and they were hugely fortunate to get through the first-half unscathed.

Chris Smalling, Paddy McNair and Tyler Blackett flanked by Antonio Valencia and Ashley Young is an almost unbelievable defensive line-up for United in such a big game yet they gradually found their poise after the interval and were able to somehow absorb the pressure, allowing United to counter-attack to telling effect. It looked a mistake from the outset yet Van Gaal and his team found a way to win.

2. The case for Arsenal having a mental block against United grows further

When asked on Friday morning, Gunners manager Arsene Wenger denied his team had any psychological barrier to overcome against United but they have now won just one of their last 15 meetings, losing 11. They were not inhibited in their play - as has often been the case - but lacked conviction in the final third during a first half they dominated and created a series of clear-cut chances.

Danny Welbeck missed a hatful of chances (Getty Images)

Danny Welbeck was among the most prominent culprits - although Wilshere also missed a sitter - and although the £16million man has impressed for England and intermittently for Arsenal, he still has just two Premier League goals to his name. Although Olivier Giroud is now fit after a broken leg - he played the final 13 minutes here - the Frenchman also has questions to answer regarding his efficiency against the top sides despite his marvellous late strike. Wayne Rooney’s clinical finishing for United’s second was an awkward contrast.

3. Jack Wilshere isn’t tall enough to headbutt Marouane Fellaini

This fixture may not have the ferocious intensity of a decade or so ago when Arsenal and United formed a duopoly at the top of the Premier League but the latest instalment was a spiky affair in which Wilshere and Fellaini provided the most controversial flashpoint.

Fellaini won a soft free-kick on the edge of the box and Wilshere, after furiously protesting at referee Mike Dean, then pushed his head into Fellaini’s chest. It was a clear motion towards the United midfielder and he was fortunate not to be sent off. Ironically, Wilshere would then have not been on the field to pick up what appeared a bad looking ankle injury in a tackle with McNair which forced him off 10 minutes into the second half.

Wilshere looked to have head butted Marouane Fellaini (Getty Images)

4. Wenger’s summer spending looks more incomplete with each passing week

Arsenal have kept just three clean sheets in the Premier League all season - against Aston Villa, Sunderland and Burnley. As much as they dominated this encounter, there was always a feeling they would prove vulnerable to a United counter-attack and Valencia’s goal was a calamity from Arsenal’s point of view. Kieran Gibbs clattered goalkeeper Wojciech Szczesny as he attempted to deal with Fellaini before deflecting Valencia’s shot into his own net.

It is an assumption that different personnel would have defended better but Arsenal have made such a habit of conceding bad goals that the decisions not sign a replacement for Thomas Vermaelen or a robust defensive midfielder continue to haunt Wenger. The boos from the home crowd at full-time were directed at the manager as much as anyone - Arsenal continued failings in the big matches do not reflect well on Wenger.

5. Robin van Persie is under pressure to justify his place

Given he spent eight years at Arsenal, Van Persie’s motivation for this game should have been self-evident but this was another subdued display from the Dutchman. With rumours persisting over his long-term future at Old Trafford, Van Persie is under pressure to produce the kind of match-winning performances that won United the title in Ferguson’s final season in charge.

There is a sense he could be vulnerable if Radamel Falcao can regain full fitness, while his 75th minute withdrawal for youngster James Wilson - with the score finely poised at 1-0 - was evidence Louis van Gaal believes the latter is now capable of handling the big occasion.