If you look at the history of these teams against each other on Tottenham's pitch, you will see that for Arsenal it is not the best place to score points, and although this has changed for the better for Arsenal in recent years, you should not take it for granted now. Because it is a derby, and as you said in a game like this, anything can happen. Like in the match against Brighton, the red card changed everything against Arsenal, and they had to settle for a draw. Tottenham are also far from their best times, but this does not mean that they cannot take points from Arsenal.
With the start of new season, things are clearly favourable for Arsenal to have good result against Tottenham in this interesting game with they are having no depth for good results against top teams like we have them into last game against Newcastle United while they fail to keep things for good result and also have poor game against newcomer Leicester City.
Arsenal is having good start despite giving points to Brighton at Emirates Stadium due to red card of Rice and their attack is also doing good but if we have any problem then things can take good change which is always on cards.
In last few games we are having some troubles for Tottenham as well but still they are doing good job and trying to keep themselves into top spots with their attacking style this game is surely going to be important for both sides as they are looking for staying into hunt for having better start of their season and keep things on good side.