By Steve Tongue
LONDON, Jan 31 (Reuters) - France Under-21 international defender Kurt Zouma joined Chelsea from St Etienne on Friday and was immediately loaned back to the Ligue 1 outfit for the rest of the season, the London club confirmed.
Zouma, 19, joined St Etienne's academy at the age of 14, turning professional in 2011 and is seen as a long-term investment by Chelsea with skipper John Terry, 33, nearing the end his long career at the club.
Chelsea confirmed on their website (www.chelseafc.com) he had signed a five-and-ahalf year contract.
Zouma has made 52 league appearances St Etienne including 12 this season but in November he was banned for 10 matches for a tackle that left the Sochaux player Thomas Guerbert with a broken leg and dislocated ankle.
A rock-solid player, Zouma was part of the France squad that won the U-20 world title last summer and was called up by coach Didier Deschamps ahead of last October's friendly against Australia but did not play.
Chelsea's manager Jose Mourinho told reporters: "He's played already a couple of seasons in the French League and many international matches at Under-21, Under-18, Under 16.
"He's a player with good potential, physically ready but one thing is to be physically ready, another thing is to be tactically ready."
Media reports put the fee at around 12.5 million pounds ($20.62 million) and he becomes the third major signing Chelsea have made during the January window.
Nemanja Matic arrived from Benfica and Mohamed Salah from Basel while Kevin de Bruyne, Juan Mata and Michael Essien have left the club.
($1 = 0.6062 British pounds) (Additiuonal reporting by Gregory Blachier; Editing by Mike Collett)