Robin van Persie has described David Luiz as "vulnerable" and claimed he would "bully" the Arsenal defender if they played against each other.
The retired former Arsenal striker was in the BT Sport studio ahead of The Gunners' FA Cup quarter-final clash with Sheffield United.
Luiz was brought back into the Arsenal starting XI despite a horror show performance against Man City last week.
The Brazilian is set to remain at the club for another season after signing a contract extension, but van Persie feels he is too culpable to an error to be relied upon.
"With David Luiz, if he was 24 or 25 you would say he is potentially world class," van Persie said. "But he is not. He is 33.
"He has all the skills too because he is confident on the ball, he can pass, he can dribble. He can defend but he just makes too many silly mistakes which makes it easy for an opponent.
"If you play against him, I would go at him, almost try to bully him and to make physical contact with him and move around him and try to tease him a little bit because he is vulnerable.
"The first job you have to do is to defend, be solid and be trustworthy. If you have extra, you can dribble, do some nice passes perfect but he needs to focus on his job."
Luiz has penned a new one-year deal at Arsenal as his current contract was due to expire in the coming days.
He has taken a significant pay cut to stay at the club however, having previously been the fifth highest earner at Arsenal on £125,000 per week.
Arsenal's technical director Edu praised Luiz as being a "really important player for us" but ex-Chelsea midfielder Joe Cole has criticised the decision to hand him a new contract.
Discussing the Man City match - where Luiz started sub - Cole said: "Arguably one of their biggest games of the season, [Mikel] Arteta left him out.
"For me that's a big signal, he's left his most experienced player out of the biggest game against Man City - and then you give him another years contract. [It's] muddled thinking."
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