That is one of Arsenal's weaknesses that is very difficult to eliminate, they always perform optimally in the middle of the season, but after that their performance slowly declines. Arsenal actually had a great chance to win the EPL trophy last season, but a mistake in one match gave Manchester City an advantage. Liverpool are very different from Arsenal, they have a winning mentality and this team has proven that they can win the title race if they attack at their best. This time Manchester City must be more careful because their rivals are no longer Arsenal.
Arsenal inconsistency is major worry because they usually play well in middle of season but struggle towards end. What happened last season against Manchester City is perfect example. On the other hand Liverpool has strong desire to win, and they show they can succeed in title races when playing at their best. Manchester City needs to be careful because Liverpool is now bigger threat than Arsenal. Competition between teams has changed and City must adjust to beat their stronger opponents. It is going to be an exciting battle for the title.
If they want to win the Premier League title, they have to keep performing consistently. There is no alternative. If you can't keep performing consistently, you won't be able to win the Premier League title. Because every season, 2/3 teams fight for the Premier League title.
In the last two seasons, we have seen Arsenal's inconsistent performance towards the end of the season, and Manchester City won the title in the end. We have seen Arsenal's inconsistent performance at the beginning of this season. And Arsenal is now 9 points behind Liverpool. This season, it will not be possible for Arsenal to compete for the title.