The Blues will undergo a major overhaul this summer with 11 players departing the club while Phil Davies will come in as director of rugby.
A host of Wales players are set to move to France this summer including Blues teammate Gethin Jenkins but Davies believes Cuthbert would be better served staying in the Principality.
"With the ball and because of his sevens experience, he's phenomenal. He's great in space and he's a natural finisher," said Davies.
"But if he goes to France and doesn't play well and people work him out defensively, all of a sudden he's not playing for the firsts' side, he languishes in the second team and gets battered every week.
"That's the decision these youngsters have to make with their agents, because I think the agents have a duty to do the best for their players.
"It's not always the money which is best. And I feel that if they develop him in France, fair enough, and look at his defensive qualities and they persevere with him and educate him, that's great.
"But in Cardiff, if he stays in Wales with the Welsh coaches, it's a question of, right, we've got to work on his defensive capabilities because the last thing he wants is to go to France and lose his confidence and then lose his [Wales] place."
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