Controversial Kakuta shines on Chelsea debut
The 18-year-old came on as a second half substitute in a 4-0 home win against struggling Wolverhampton Wanderers.
Chelsea were barred by world soccer's governing body FIFA in September from signing new players until 2011 after being found guilty of inducing Kakuta to break his contract with the French club in 2007 but that ruling is now on hold pending appeal.
Midfielder Kakuta, who had been at Lens since he was eight years old, was also handed a four-month ban from competitive matches and ordered to pay 780,000 euros compensation jointly with Chelsea.
"Kakuta is a good talent, he is very young. I think that he deserved to play today," Chelsea manager Carlo Ancelotti told Sky Sports.
"He's training very well...when there's a possibility I like to put (young players) on the pitch in the first team."
Kakuta got his chance when he replaced Nicolas Anelka after a spate of injuries to regular first team players, including Frank Lampard, Deco, Didier Drogba and Michael Ballack.