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.
"He is physically OK but we'll see what will happen," Hiddink said of Miazga. "He's a youngster, although already in the USA national team, but he has to get used to our way of playing -- it's a little bit faster. But once he adapts himself he's an open guy, a good guy, very professional.
"He has moved up and I have a kid from the academy [Clarke-Salter] who is now with us. We'll see what will happen but we have inside the first squad of 15, 16 players some variations with [Branislav] Ivanovic, with Baba [Rahman]. We have some options to use.
"We don't have any doubts about whether [Miazga] is needed. He was meant to come here [in January] to get used to our way of working, training, so that he could integrate more easily and not just in the upcoming season."
Zouma had made more Premier League appearances than both John Terry and Gary Cahill this season, establishing himself as a key figure and fan favourite at Stamford Bridge, and Hiddink described the Frenchman's injury setback as "a sporting tragedy."
"I called him just a few hours before his operation when he was in Barcelona and I tried to encourage him, saying 'things happen' and so on, but surprisingly he was in a mood as if nothing had happened," Hiddink said of Zouma. "He was confident.
"His operation went well but it's tough. He's out for months and it's a sporting tragedy for him, just in a period where I think he was improving on all aspects of his game.
"He's not able to play in the Champions League in France, not able to be a candidate for the Euros, so it's a tough time for the player in his career."