So you just like to argue for arguments sake? Fine, lets say he is not "made of glass" because you dont like how that sounds. It doesnt change the fact that he is over thirty, it doesnt change the fact that he missed 25 games last season and it doesnt change the fact that he is coming off a serious injury where he has been out of action for over 100 days, an injury with the potential of niggling him over the course of the season.
Nevertheless, even if we would live in a magic land where no one ever gets injured again, we still need a fourth starting level CM due to rotational reasons.