That'd be for one game though. Even though Stones has been out injured it is clear to see who your preferred options are at the back. Stones will probably play in the cups with the odd league appearance when you focus on the latter stages of the CL for me that means he's a backup.There's a difference between being a back-up and not starting a game.
Say you start your game against Sevilla with a mind on the weekend fixtures, so you rest Martial. Rasford, Mata and Sanchez behind Lukaku. Does that suddenly make Martial a back-up? Of course it doesn't.