With someone like Grealish there is an increased risk what would be a red flag for him, would be his lmited mins in the last year, to ask him to go from 0 - 100 mph - Weds - Sat would be a concern for a sports science team TBH.
You are right though you can manage the risk, so hypothetically for the debate, you manage his mins in the Derby so he plays the full game Vs Wolves - if your priority is the League Cup - sure.
You manage injuries when they over mate, you deal with preventing injuries every week, Illy's mins are often manged for example. Idrissas more so to, ive noticed.