Walker played only for his pace.
If England had a pacey CB, someone like our Sanchez, Walker wouldnt be in the first 11.
If Joe Gomez was fit, he might take the right-sided centre-half position.
As for Trippier, I'd like us to go 3 at the back anyway, but I think it especially suits our fullbacks and footballing centre-halves (Vert and Toby, maybe Foyth). I also think Dele and Eriksen find better spaces in the setup. IMO, our best team right now would be:
----------------lloris
-------toby---sanchez---vert
trippier------wanyama--------davies
----------eriksen-----dele
-----------------son
----------------kane