Yeah they are definitely the favorites to win the game, but an upset can happen as Arsenal are currently losing 1-0. There is still quite a lot of time in this game for things to change, but for now West Ham are looking pretty decent in what they are doing, they are strong in defense and when they do go forward, they are causing problems for the Gunners. If West Ham continue in this way, then theu have a chance in this game, but Arsenal are going to test them so much.