There are a couple of questions that keep being asked in this thread, so rather than quote a random one I'll just make the responses here:
Question - Why is Jose talking about rotating Jones, Lindelof and Rojo in regards to the World Cup at the expense of Bailly, but not Martial and Rashford when Sanchez is in the same situation as Bailly?
Answer - He's obviously not going to deliberately weaken the team. It indicates that he likely considers Jones, Lindelof, Rojo and Bailly to be around the same level, so favouring the ones who may go to the World Cup won't really change the strength of the team (although if Rojo doesn't start getting games then he's probably at a lower ranking). Whereas obviously he feels that the team is stronger with Sanchez playing ahead of Martial and Rashford, so he does that. Meanwhile, the fact that Smalling simply plays every game and isn't being rotated indicates that Mourinho considers him his #1 central defender that he can trust to stay solid while his partners continually change.
Hopefully Martial's good performance off the bench against Arsenal will see him push into the team. Especially with Lukaku also now out, he may get a chance to cement his place again.
Question - Why does it seem Southgate won't take Smalling?
Answer - The reasons to this decision have been talked about (Smalling's lack of ability on the ball), and although I don't agree with them I will say it's fair for the manager to choose to make that stand for his starting line-up. If you want to attempt to play to that style then the other defenders may suit it better. However, it is absolutely ridiculous not to take him at all, as there will be games where that plan won't work simply because the other teams are better (particularly in the midfield area which is the most important to that style of play), and in those games you may end up needing the best pure defenders that you have. And Smalling is far ahead of the rest of the options in that regard.