Some people point to the fact that we didn't do very well in 4-5-1 in the second half, as evidence for the outcome not being about systems. Or at least not about 4-4-2 vs 4-5-1/ However, there are several problems with this argument.
1. In reality we didn't play 4-5-1 for most of the second half, but what looked like 4-3-3 much of the time with VdV and Bale way up the pitch. Worse, and imprtantly, both VDV and Bale played narrow instead of wide so we didn't attack their full backs or support our own.
2. Because we went behind so quickly in the second half we were chasing the game in a supposed 4-5-1, so it was the wrong formation at that point in the game anyway. Not that we stuck to it.
3. in the 4-4-2, although we went 2-0 up, the balance of play had alraedy moved against us from about halfway through the first half, and we never looked like we controlled the midfield, or exploited the flanks effectively. Arsenal targeted Benny very effectively, and Walker slightly less effectiely, who were both unprotected most of the game.
4. To deal with a team like Arsenal away, you have to a) neutralise the 3 CM superiority with 3 CMs b) neutralise, psychologically and in reality, their pace down the flanks -with your own pace c) keep RVP quiet. We failed to do any of these.
Even at 2-0 up I felt we stood good chance of losing unless we changed things around -particularly playing Bale and Lennon wide and going three CMs -and that is what Harry should have done at 2-0 up. At 2-0 up I took 10-1 on an Arsenal win. I'd have preferred to have been proved wrong, but I'm sure I wasn't the only one who read the game that way.
Other factors like the yellow cards, and some of the player's attitudes didn't help, but I think poor tactics were the main reason for yesterday's shambles.