Don't really get some of the hate for him on here, he's a very reliable CB. He has made a couple of mistakes and been physically lacking at times, thinking of the Crystal Palace and Southampton games at the moment.
The problem is, we don't control games nor do we score, every mistake and goal is scrutinised to the very last because it usually costs us the game. If we were winning games 2-1 and 3-1, we would barely even be looking at these. In reality, what costs us results is our inability to dominate teams and create goalscoring opportunities. We find ourselves on the back foot over and over again, and invite pressure which inevitably leads to mistakes and goals conceded.
He might not be good enough to get us back to the top in the long run, but defence definitely isn't one of the areas we need to strengthen at the moment.