LONDON -- Chelsea's new centre-back Matt Miazga is not yet ready to fill the void created by Kurt Zouma's season-ending injury, manager Guus Hiddink says.

Jake Clarke-Salter, 18, will move up from the academy to bolster Chelsea's first-team defensive ranks for the rest of the season.

Zouma will be sidelined for around six months after undergoing surgery on a ruptured anterior cruciate ligament sustained during Sunday's 1-1 draw with Manchester United, ruling him out for the rest of Chelsea's season and Didier Deschamps' France squad for Euro 2016.

United States international Miazga, a January signing from the New York Red Bulls, is doing double training sessions at Cobham to improve his fitness levels while Clarke-Salter will now train with the first-team squad on a regular basis, but Hiddink says he regards both as long-term development projects.