I think that GSP's problem is that he doesn't go for the chin. Just look at Fitch and Kos after their fights with him, they both had black eyes and bruising all over their heads. You just aren't going to KO tough opponants like that jabbing them in the eye over and over. Soften them up, sure.... but a KO would be unlikely. If you watch Anderson and Fedor closely they go for the chin a lot more, and with better results. This content is protected and This content is protected VS This content is protected Anderson taps Griffin on the chin and so does Fedor against Rogers while GSP hits Penn in the eye/nose area. Big difference in results. I'm not saying that GSP doesn't have KO power, but he does not actively get KOs and that this is the reason.
It's mostly because GSP very rarely uses uppercuts and short up-close hooks. He's stopped using his headkicks and spinning backfists too. I can't really say I blame him. It's dumb to trade with guys like Thiago Alves or even Josh Koscheck, but I think it makes a more renowned statement beating a Fitch or a Koscheck at their own game, it shows how far ahead GSP is infront of these guys whose speciality is the ground game. He'll do the exact same thing to Jake Shields, bar injury or lack of motivation, no question.
its like in the Khan fight Maidana was clubbing him all over the head and Khan was taking them well then in the 10th one of those looping shots caught his chin and he was ****ed and was lucky to survive.
The other two are throwing straight rights; GSP is throwing a superman jab, he was not intending to KO his opponent there.
His technique, timing, distance and accuracy are all things that he needs to work on and Roach is excellent for that.