You do realise if he has niggles, then playing him in the SANFL will give you a similar risk of injuries compared with playing in AFL?He's in his first year, any games he plays at AFL level is a bonus. you dont take risks with him!!
It’s only when he’s obviously injured where he can’t train, then he should be rested from playing. If he’s out of form or not with it mentally, then another small forward should take his place. The team selection and injury prevention are sort of separate issues.