That's not a lot different from other teams banking on their star players being fit/available 'all' season either!
Pretty sure most teams expect some sort of outage, if not from injury, then card accumulation!
Id suggest arsenal have a history with regular injures to certain players so if they don't over fill the squad a bit, surely it comes down to bad management?
obviosuly all team hope for a fully fit squad but players will be missing. The skill is to have a squad good eniugh. Which IMO arsenal still don't to mount a realistic assault on the title.