I didn't get to see the match yesterday. I just watched the replay.
IMO Arsenal lost on these accounts:
1. Mistakes in their own half: Ozil pass to Fernandinho, Navas' pass went through Monreal/Vermaelen, Gnabry passing to Fernandinho...
2. Left side of play: Monreal and Wilshere were awful.
3. Giroud can't finish
4. Ozil playing in the middle as the No 10. Better when he's playing on the right.
5. Wenger subbing Flamini. You can't play without a DM.
I wouldn't blame the team much though. It's been a difficult week of football.
Walcott should start at Chelsea. Arteta, Gibbs, Cazorla and Bendtner too.
Set out to correct the world's wrongs and you will most certainly wind up adding to them.