Kakuta made an impressive Premiership debut for Chelsea in their victory over Wolves last week.
"He's very young and nobody makes such a big story of him," Wenger told arsenal.com. "You also have to be a little bit cautious. He has played half an hour against Wolves! Before you needed to play five years, after that one year, now ten minutes [to make your reputation].
"He's a guy I don't know. I know his name and I know that he played in the same squad as [Gilles] Sunu in the French national team. We knew him but he was in Lens and I thought he was well protected there. I was surprised when he went to Chelsea."