Tomas Kalas
Kalas has been on the books at Stamford Bridge for two years but has spent that entire time on-loan in the Netherlands with Vitesse Arnhem.
The Czech Republic international is still just 20 but has played 76 competitive matches for Vitesse and has looked very promising at centre-half.
The youngster will certainly be behind Terry, Gary Cahill and David Luiz in the pecking order next term but should be given a chance by Mourinho.
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