Pundit lays into Arsenal centre-back.
Luiz had a poor game at the weekend as Arsenal lost 3-1 away to Liverpool.
Cascarino says he believes Luiz cannot be trusted to play as part of a four man defence.
He told The Times: "I don’t think you can play a back four with David Luiz — watching him one-on-one with Mohamed Salah was laughable.
"Emery spent £135 million this summer and they may be better but still looked naive and limited in terms of shape and system. They are still a long way off the top two."
Its tough to get too hung up on Arsenal's defeat to Liverpool, the Reds are arguably the best team in Europe right now.
Luiz is still adjusting to Arsenal, his new manager and teammates.
The Brazilian sent a message on social media expressing his desire to improve.
View this post on Instagram
Life is tough and football is tough also sometimes !!! But I know one thing , I will never give up !! Was always like that my life ... I came here with a goal , and I will fight until the end for that !!! Thank u for the fans , for all the support !!! I will never hide , wining or losing !!!
Fortunately Luiz does not have to play away to Liverpool every week, but Arsenal's next game is another high pressure one.
It is his first North London derby as Arsenal host Tottenham.
He needs to show improvement and start proving his doubters wrong.
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