That is the opinion of former Arsenal star and Chelsea fan Paul Merson.
Luiz switched the Blues for the Gunners on transfer deadline day for a fee of around £8million.
The Brazilian made 50 appearances in all competitions last season under Maurizio Sarri but new boss Frank Lampard was happy enough to let him leave Stamford Bridge.
However, Merson has questioned the decision of improving an “enemy” in Arsenal.
And he says Chelsea are now left with centre-backs who are not as comfortable on the ball as Luiz.
“He’s let David Luiz go and he’s strengthened an enemy, an arch enemy of his, who are fighting for a top-four place,” Merson said on The Debate.
“I go to Chelsea, I go and watch Chelsea.
“They play out from the back – he’s he only one that plays it, he’s the only one who’s comfortable on the ball.
“The others aren’t comfortable.
“Emerson’s comfortable but Emerson played half the game last year.
“So you’re asking [Kurt] Zouma to pass the ball out, which he’s not up to at the moment, he’s just got back into the team.”
Merson reckons Luiz will help Arsenal in their quest for a top-four spot.
“I think David Luiz is an unbelievable signing,” he added.
“The lad can play, he can hit a 70 to 80-yard diagonal ball to anybody on the pitch.
“He can find players, he’ll score goals.
“I think they’re right in the mix for a top-four place, I really do.”