Had a day to think about the match. It was an interesting game that told both sets of fans a lot about their teams.
Before the game, I think every Arsenal fan was hoping for the best and expecting the worse. We do seem to have a mental block at Old Trafford and we make it easy for you almost every time. From a logical perspective, many of our fans think we are the better team and therefore, should have a good chance of winning. In the end, the result was a good one for us.. mostly because of the circumstances of the game.
From an Arsenal perspective: We were utterly garbage. The worst performance I've seen from us in any competitive fixture since the 8-2 game. It's worrying for us because it shows that not only that the mental block does, indeed, exist at this ground but also that it's still alive and well even when we have been the better team for ~4 years now. I think we showed naivety and worry. The cool, competitive and pragmatic nature of an elite team continues to elude us and our title race will fall as a result of this unless we sort it out. Although some of the newer heads to our first team (Mustafi, Elneny, Coquelin) do show the fight and mettle required - even though the defending of the latter two was quite poor for your goal.
From a United perspective: I think the outlook is even more bleak than it is for us in terms of this season. This was a massive opportunity for you guys against an Arsenal team lacking in energy, commitment and belief. An opportunity to beat Arsenal doesn't come much easier than this. (we played better in all the games that you've won against us recently than we did yesterday) I'm surprised it was possible to find a way to mess it up, honestly. I think it may have been a different story should Zlatan have played.. but on the same note I could say that about Cazorla or Bellerin for ourselves.
For you guys to get Champions League football, you'll need to finish higher than 2 of Chelsea, Arsenal, City, Liverpool and Spurs. At this moment, I just can't see that happening. City and Chelsea demonstrated that they are currently a class above United in the league. You did, to be fair, get a good result against Liverpool in a disciplined performance. I don't think this was a positive result for United, though.. given simply how bad we were.
So, yeah. The game was an interesting one. Conservative. The casual, neutral fan may say 'boring' but I enjoyed it. And I don't think either set of fans can come out of it with too many positives.