Honestly, Terry was once the best the league had but I don't think so anymore, and Cahill has never been world class. The attack and midfield in this team are looking superb - ironically it is the defence that looks in need of a rethink. Hummels would be fantastic, as would Varane. If our defensive troubles continue Zouma might end up playing. Poor Courtois is getting very sketchy cover at times.
Zouma might actually be the hidden gem that becomes Joses Varane at Chelsea. Varane was never expected to play with Pepe and Ramos at Madrid but Jose gave him a chance and he took it. Jose has shown he is not afraid to ditch experience if a youngster can take his chance.
I have never rated Cahill that highly anyway, so why not change both CB's