At 0-0 when Wilshere was injured, I think it was a logical sub to bring Cazorla on for him; I say that because we dominated the game, and at that point looked a lot more likely to get that first goal.
However, when we are bringing Giroud on at 0-1, already with Cazorla on the pitch, the logical move for me would have been what I mentioned above, but at the same time tell Cazorla to play deep next to Arteta and help him PROTECT THE EFFIN' CBs!!!!
We see this time and again when we go a goal down; all of a sudden it seems as if everyone, bar Arteta or Flamini, has COMPLETE freedom to push as high up the pitch as they want. Today, we even saw Mertesacker ON THE RIGHT WING FFS! The truth is, most of the time, that we don't need more players pushing up. Especially today it was soooo obvious that we easily worked the ball into their final third, and we could get crosses into the box at will. We needed another player with good aerial ability in the box to improve our percentages, but Wenger completely got it wrong with how he utilized his players when Giroud came on.