Full backs need to do most running in this system, so I guess rotating players for a midweeker may be the reason.
I reckon you’re right. Full backs need to provide the width and support the attackers a lot in this formation - a bit like the old Roberto Carlos / Cafu role for Brazil. Reckon Fryers and Yiadom just rested. Big call resting Yids. Fingers crossed it works as Cavare looks good going forward but slightly less reliable than Yiadom defensively.