I think he was really poor defensively, largely owing to the size difference, Sunday.
I also think that Emery has developed a machine and when we alter constituent parts, the impact is detrimental elsewhere. Mings playing alongside him does not help as he is too slow, ponderous and poor in distribution, so there is nothing to keep an opponent occupied beyond pressing Maatsen. Doesn't entirely excuse his poor performance and doesn't excuse it attack wise at all, but its a factor.