Players will be rotated, but there will be a first xi in rdz's head. When the big games come along you must know your best side. And I think RdZ has a group who he trusts to perform over others. He effectively admitted that having frozen Gilmour out for much of the season and was almost forced...
Yes, I think he is a better defender than Webster. I don't know enough about Igor to know whether he will be a definite starter or not.
I think RdZ will always find a position for Gross, and at the moment right back is his most likely position.
Pervis is a definite starter as well I am sure. Which is where I started from, and then think the rest get rotated around, but suspect Solly is also a starter when fit. He has also shown a lot of faith in Mitoma, and will start him as much as possible.
Trying to figure out what would be Roberto's go to first eleven if all players are fit.
Working on the assumption that no more major ins and outs, I think RDZs absolute certainties to start are:
Dunk, Caicedo, Gross, Lallana, Pervis. (RdZ always picks Gross and Lallana if they are available)...