He is quite old by the way. He is 38 now and he is currently the most experienced defender in the team now. I believe that Silva is still a very useful defender for Chelsea side. Silva and Badiashile are making a good duo in the lineup these days. They haven't conceded a goal with this duo these days. I think that it is always better to have at least one of their centre-backs as an experienced one. Otherwise the problems might get bigger by simple mistakes.
He's so much experienced at defending, he literally saw that during the FIFA World Cup. He's also formed a good bond with Badiashile who was recently added to Chelsea squad. I'm sure he'll pass so much knowledge into the defender to help coordinate the defense when he's absent.
Koullibaly doesn't calculate, he thinks it's all about physically minded, and he overlaps a lot. I don't see him finding his way back Into the first team. Good deal by the way, Thiago Silva should be given an extension.
They can obviously increase the contract. Of course, they can give him one more year of the contract. I think at this point we all know that it is kind of a bad decision to keep a player who is more than 38 and there is obviously some player who is going to take his place very soon.
But until that happens I think he can stay. A contract of one more year is not going to hurt too much for Chelsea. Especially since they are spending so much money and still not getting any results.