McClellan was a physical beast at 160. Unfortunately, it is likely his enormous weight cutting played a part in his unfortunate brain injury.
I've heard he complained about headaches after the Julian Jackson bouts? I've also heard he would go to war in sparring, believe there's footage out there of him and other Kronk fighters going at it hard. I imagine what happened to him was cumulative though that's just a guess, I'm not a doctor. Sad to think about what happens to fighters who train and live like that, guys like Terry Norris or Meldrick Taylor.