Don't want to get too deep into this, but that's not really how it actually is on the pitch when Ramsey is playing. Ramsey plays like a central mid in possession, albeit with a slight preference to the right. In defense he defends centrally a lot, but he is also the primary support for our RB. He plays the role exactly like Pogba is playing the role for Juventus.
Now, we don't fully employ the diamond midfield because we do it differently on the left side with Cazorla and Alexis. It is natural, perhaps, because Cazorla is a lot less dynamic than Ramsey is; I don't think he would cope. I think it is clear as day that we have struggled in central midfield without Ramsey in the team btw.
