Lazy Rooster?

I've been noticing some strange behavior from a BLRW rooster that we have, I almost wanted to post this in injuries/diseases... Anyways, the guy's just sitting down everywhere. He's the top rooster out of 3 and he gets his food and has his ladies and whatnot, so I don't know if he's just too complacent with that or what, but it really seems like he's having a hard time standing. He walks sort of normal, but then will stumble, and kind of scoot backwards into a sitting position, then just stays there for a while. He basically never stands anymore. This has been going on for maybe a week, and seems to be getting worse, to the point where he will barely stand up or walk away when I approach him. Previous to this he has never wanted anything to do with me, and now I can just walk up to him a pick him up. I can't see anything physically wrong with him, soo..... Anybody know what this could be? Some kind of chicken genetic disorder? BTW, He is approx. 9 months old, if that's relevant.