9 yrs old? I wonder if age has anything to do with it. Like, perhaps he's developing a skin condition? Can you peal any of it off? I had a Silkie who lost a patch skin with the feathers still on it. Nothing bled and I couldn't find an injury. It was weird and made no sense, but I'm questioning...
Can you check him for mites and lice to rule those out? Have you had any recent predator attacks, seen blood on coop floor, or had any bullying issues? Do you have any other roosters? To me it looks like an injury. He could be overmated by another rooster if you have others.