I think the Arsenal/ Chelsea game will be an arsenal win or a draw. Cant see chelsea beating arsenal. History is irrelevant in this game. Given the poor form chelsea are in, Mourinho might just want to avoid a hiding from arsenal and will probably opt to ring-fence his 'ego' by going for a draw. I will be surprised if he goes for end-to-end stuff. He'll probably keep possession, park-the-van and either do route 1 or counter.
Chelsea have been extremely poor. One just needs to review the last 4 games and see a dreadful run of defeats, draws and very narrow wins.
This season arsenal are different and have kind of 'toughened' up. So if arsenal play their game without fear, they should win. Further there is no drogba to cause wenger grief. Given that chelsea are in a moment of weakness and their opponents flying high, I expect Mourinho to avoid 'the battle' on monday like he did in the game against man-u at the start of the season.

I am also thinking Chelsea migh not win this encounter...they lack rhythim!!!!