It bothers me slightly, but again, DS does not arrange friendlies. DS does not undertake HR or deal with player liaison. He is not responsible for arranging flights, arranging player relocation, etc etc. You are also making an assumption regarding the injuries result from poor physical preparation, when they could be the result of a whole host of other reasons.
I think some people assume that because he's our head coach DS is involved in every aspect of the club. That may have been more the case in the past when things were less professional, but DS is a Head Coach, who works with a DoF, and a host of behind the scenes staff who Dean has no control over hiring/firing, I think it's pretty harsh to throw shade at DS for what is a collaborative effort.