Cafu Santos headbut knockout

So I was watching this video looking at the poor guy in the blue shorts (Gledson) getting belted by Santos and at just under 1minute in it looks like he's treading water. He's tied up by Cafu against the wall and it looks like he wants to create some breathing space for himself but Santos is relentless. His knee digs and punches are getting through. Gledson is using his limbs to defend so he's holding out but Cafu sees this and uses his head. No, really, he uses his *head* to butt into Gledson. Gledson neutralises the potential of a next head butt by pushing Cafu away with his arm, but now he is one limb 'down' on his opponent and can't stop everything and receives a dead leg for his trouble. At this Gledson winces and tries to draw breath. Cafu must feel his opponent weaken, pulls back his head and butts Gledson again, this time sending him to the floor, knocked out.

I suppose head butts can be difficult to pull off as if it's not done well and properly you risk damaging your own head but this guy really pulled it off, fought strategically and used his head to strike hard at the moment when his opponent had eased off.