Rhys Williams is doing far better than he should be considering the level of football he was used to. His problem and the teams problem is that with Fabinho in central defence it means we're missing Fabinho from defensive midfield as Henderson and the rest of the midfielders just don't play the position as well as he does.
They are all good players but Fabinho is just better at anticipating danger rather than reacting to it when it's too late. Our defence looks more vulnerable when the opposition has the chance to play dangerous passes to their forward players and Fabinho normally stops that at source. I think we'll get better when Fabinho is back at defensive midfield even though he's been phenomenal in defence. That's the knock on effect of Van Dijk being injured and Matip and Gomez being injury prone.
This is it. Buying a centre half won’t fix this. Anyone coming in will just replace Williams as Matip will break down again in a few weeks. Fabinho will still play at the back.