1. United lack midfield creativity
n the first half Van Gaal set his side out in a 4-3-3 with Daley Blind at the base of midfield and Marouane Fellaini and Ander Herrera either side of him in the shuttling midfield roles. United started the game off attacking well enough in this shape. Herrera would create overloads in his right-sided center midfield position with Angel Di Maria down the right channel. Di Maria would cut back onto his left foot and swing crosses towards the back post where Fellaini continually tried to push forward onto Arsenal's left back Hector Bellerin and use his height advantage to win headers. United were fairly bright going forward and equalized after Nacho Monreal's opener for Arsenal from a Di Maria whipped cross to Rooney.
The issue with Van Gaal's 4-3-3 was in defense. With Herrera and Fellaini both shuttling forward into advanced positions, Manchester United were left too open in the center of the pitch when Arsenal won the ball back. Blind was left to defend counterattacks on his own and Arsenal proved dangerous breaking into that space quickly on the counter.
Recognizing United were probably too open, Van Gaal replaced Herrera with Michael Carrick at half time. Carrick sat deeper than Herrera had closer to Blind while Fellaini stayed high up the pitch. United had essentially switched to 4-4-2. While this served to keep United more compact defensively, it also meant they were short on creativity in the middle of the pitch. Whereas a player like David Silva can provide creativity in Manchester City's version of 4-4-2 by tucking inside into gaps of space from the left, both United wide men Di Maria and Young maintained positions in the channels. Fellaini got high up the pitch to win direct balls with Rooney alongside him to get on the end of knock downs. This meant United didn't have a player getting into the gaps of space between the Arsenal center midfielders and center backs. Their only link to the attacking third therefore was through overlapping runs in the channels between fullbacks and wingers and then hitting crosses towards Rooney and Fellaini into the box. In that respect this resembled a United performance under David Moyes.
There's certainly nothing wrong with getting the ball wide and aiming at a big target in the box- it's a strategy Arsenal aren't always convincing defending against. However, with Arsenal employing a tremendously attacking side, a more creative center attacking midfielder would likely have found space to influence the contest. I thought this game was crying out for the introduction of Juan Mata, a player whose clever positioning would have made the still relatively inexperienced Francis Coquelin's day much more difficult. As it turned out, Coquelin didn't have a direct opponent in the second half in midfield and was therefore able to offer cover where needed. This performance will do little to silence critics of Van Gaal's formation tinkering and overall tactics.
2. This was a typically English and typically FA Cup type game
It was entertaining, open, frenetic and often a little sloppy. The crowd roared as the sides took turns attacking one another at speed. Neither side ever really developed any sort of control on the game and in that sense it was a distinctly English game. Nowhere else in Europe's biggest leagues would you witness a game that remained so open without one of the sides making a change to bring some sort of order to proceedings. It was probably fitting that the winner came from a bad individual error- neither side were especially well organized and it was one won by the ability of the individual players rather than a tactical system.
3. United's form worrying
United's next five league games include visits to Tottenham and Chelsea and home clashes with rivals Liverpool and Manchester City. Those five matches will go a long way in determining whether United will secure a place in the Champions League and should bring to light whether the club has improved under Van Gaal. While league wins over Arsenal in November and Liverpool in December were important, they weren't exactly commanding performances. United have yet to put in a truly commanding performance against a top side this season. Five of their final ten fixtures are against opposition currently in the top six. Uninspiring victories over Sunderland and Newcastle in their last two league games after defeat to Swansea mean United aren't exactly experiencing the run of form you'd hope heading into the final months of the season. They'll again face Arsenal at home in the second to last weekend of the league. Van Gaal has his work cut out.