Arsenal, Liverpool and Chelsea are considered the hot favorites for this year's Premier League title. So, if Arsenal wanted to stay ahead in the title race, they would have to earn points against Liverpool. Arsenal has already fallen behind in the title race due to the defeat in this match.
Arsenal losing to Liverpool is really not the end for them and I still see them as a serious contender. They really did not played badly in that match and I think it's a balanced match that could have gone either ways, but Liverpool won it with a goal deserving of a win.
Arsenal has not lost to the big six in the last to seasons till this match, so I don't think this losing will define their season, but it would have been a statement for them.if they had won at Liverpool, but the lose still does not make them.less a contender.
You are right that Arsenal are one of the most worthy contenders for the Premier league title despite their defeat against liverpool. And they still have the ability to occupy the top spot of the table. There is no doubt that the title fight will be more intense this season in the Premier League.
Anyway, I am keeping Manchester City and Manchester united out of the title fight. United are still fighting hard to stabilize their squad. Their overall performance is still very erratic. Especially their defense is quite weak. On the other hand, Manchester City will be behind due to the erratic performance of their attacking players.