The Hammers have conceded 11 goals in their last five matches with back-to-back defeats by Newcastle and Chelsea denting their bid to reach the Champions League.
When asked why West Ham’s previously excellent defensive record has been blemished of late, Moyes had a simple answer.
“Mostly it is not having Declan Rice,” said the Hammers manager.
“Is he that important? I think so, yeah. He played in the game where we drew 3-3 against Arsenal so you could take that away, but he is incredibly important.