I really don't think he had much left to give, or ever had much to offer. Carwin started way, way too late in his life to ever really make a long term impact. The only reason he even made the shockwave he did is because the UFC HW has always been by far the thinnest division in terms of talent. The reason p4p rankings exist is because of weak divisions such as HW that rarely showcase as much technical skill as the other divisions.
I agree with this. I'm not trying to hate on Carwin, but people sort of expected too much out of him. His best win was Mir, a guy who sucks vs. big strong punchers who muscle him around. He beat Gonzo, who was cut. He beat up Lesnar, but we soon found out Lesnar isn't all that, and can't take much of a punch.
Carwin has massive power, but is slow as death. Solid wrestling. No cardio at all. Not much BJJ. His size was exaggerated, they said 6'4 at one point, he is no more than 6 foot.
HW can use any solid fighters they can find. But Carwin is 38, he simply started too late, and I think he was roided up badly when he started.
If he fought guys like Werdum, Cain, Hunt, Browne, Roy he would have got beat up like he did vs. JDS. Carwin had power, but his striking wasn't good.