Ex-Chelsea star Frank Lebeouf thinks David Luiz is a "fantastic" player but believes the Stamford Bridge centre-half takes "too many risks".
Luiz was at fault for Cardiff's opening goal against Chelsea at Stamford Bridge on Saturday.
The Brazilian misjudged the ball and allowed Jordan Mutch to latch on to a through pass, despite being well positioned to intercept it.
But while Leboeuf admits Luiz commits too many mental mistakes at the moment, he is backing the talented Chelsea defender to get it right.
"Sometimes he scares me a little when I see him being very easy and taking too many risks, but he's the same kind of player I was," Leboeuf told Goal.com.
"Maybe I was less crazy than he is, but he's a fantastic player, he likes to go forward, and I can't reject a player like that because that's the philosophy I like.
"But at the same time, if you're going to play him, you need to make sure people compensate, and one of the midfielders goes next to John Terry when he goes forward.
"It's teamwork, and David Luiz has to be careful that someone can take his place when he does things. I like David Luiz - he brought so much to the club and he's a talented player.
"He has to work on the defensive aspects of his football, but a little bit of craziness doesn't kill anybody, and it brings a bit of flavour to football."
Luiz appears to be Jose Mourinho's preferred centre-back partner for John Terry, with Gary Cahill so far making do with a place on the Chelsea bench.
The Brazil international was briefly deployed in a defensive midfield position last season, with many pundits suggesting it could be his best position long-term.
But Luiz was exceptional for Brazil at the Confederations Cup in defence, and will almost certainly start for his country in central defence at the World Cup next summer.