Maybe Mullen shares Hevesy's coaching style. I say this because I talked to a former offensive line starter under Hevesy, and he said Hevesy was a terrible coach and *******. He said (in so many words) "we had a couple good young guys that should have developed into good linemen, but Hevesy road their asses so hard, that I think he got in their heads, and they just didn't pan out."
Maybe they just weren't good enough, but this guy's comments rang very true to some of the comments/rumors I've read on message boards. So maybe that's a common coaching theme in Mullen's clan.