I think 'he has to play' he means he must be a first team player. Stevens, Fleming, Whittaker (probably) and O'Grady (again probably) are new players who will be squad players pushing their way into the first team (like Smalley) and are not certain to start the season.
I think SC will want Shez to be convinced that he is good enough to be a first team regular like Allott, Eardley, Davies etc when the season starts.
I doubt he will have to play every week even if Shez wants to change system or he dips in form.