Our record in the big games (City, Chelsea, Man ure and Liverpool-ish-) is really bad and we needed to win at a big away ground to sooner or later to prove out worth and we did that. Spuds are a beter side this season but its a local derby and anything can happen, we were absent on the day and thats why i dont think it was significant.
Its also worth noting that you need a bit of luck to go your way and yesterday we didnt really have that (their first goal for example, the ball fell to their best player).
All in all, i think we will show consistancy as we always do in the 2nd half of the season and Wenger knows his precious 4th place is in danger of slipping away so he'll do whats required.