I think part of the problem is that Coquelin and Cazorla work best as a package, and fill in the blanks in each other's games really well - the two of them together is a beautiful thing, but lose one and you kind of lose the whole attacking or defensive side of the heart of the team. Given the frequency and severity of the injuries we pick up, that's a worry.
With players like Xhaka, Elneny, and dare I say Wilshere, if he's ever fit (and played in the right place), I think we're looking at more independent, rounded players - none of them may be quite the passer that Cazorla is, or quite as efficient a tackler and interceptor as Coq is, but they're all competent or better in both areas, and I think each of them would probably cope with the loss of any given partner a little easier?