My thinking is - we extended Yaya for a reason. We have a target in mind at DM but he's obviously not immediately available. Fabinho doesn't fit the bill that Pep requires, yet Yaya did an adequate job in the position to the point that, perhaps, a rotation with Fernandinho could be enough in the short term.
I don't think we're really in on Carvalho, but we'll see.
Completely agree on Yaya, it wouldn't have been for sentimental reasons.