That's football for you. Always expect things like that once in a while. Although looking at various aspect to judge this match, Arsenal has all it takes for a successful win. My most surprise is how Newcastle could defeated them without a goal.
Newcastle have a really tough defense for Arsenal in the EFL Cup this season so in the first leg and also in the second leg of the EFL Cup competition Arsenal really couldn't score against Newcastle and that has indeed made some people very surprised at Arsenal's performance. But Newcastle also still can't be sure of winning the competition if Liverpool successfully make it to the final and face Newcastle to show who is the best in the EFL Cup competition this season.
I knew arsenal will lose this match because they are never consistent, some people where saying arsenal will win Newcastle united because they won Manchester city, arsenal is a club that are never consistent they may win a match today and lose a match tomorrow even to an uninformed team, I really don't see them lifting any trophy this season because they are not ready for it, I most say that Newcastle united has a very strong defense they should keep it up, there problem too is lack of consistency, even with the strong defense arsenal could have still scored and that is why I always say arsenal needs a very good striker a striker that will give them goals, if they had a good striker they would have scored in that match, some strikers will break a very strong defense and score a goal and that is what arsenal needs right now and also they need to make there defense more stronger if there defense was strong Newcastle won't have seen an opportunity to score and the game could have ended in a draw, so since they don't have a good striker available for now they should make there defense stronger.