Yeah Chael has made some comments about it throughout the years but im not sure if the full story was ever brought to light. Here is one comment i found doing a quick search
"I challenged Rich for 18 months, and he never responded," said Sonnen. "I challenged Anderson Silva for four years and he ducked me every bit of the way. I challenged both of those guys and in the process I fought 12 guys in the Top 10, beat 10 of them, beat every champion in every organization there's ever been... I beat the Elite XC champion, I've beaten the Strikeforce champion, I beat Bodog's champion, I beat IFL's champion, I beat the WEC champion twice. I beat every champion in every company that's ever been, and there's not another middleweight living today that can make that claim, except for the UFC champion and the math teacher wouldn't fight me, and neither would the "Spider." But he's here now, and he's not here on his own free will. He's here because Uncle Dana made him do it."
But he has made other comments also. I think it was a camp vs camp thing and Matt Lindland was at the center of it but i dont know.
What Camp is Rich with btw??? For some reason the only person i know who trains with Rich is Jorge Gurgel lol.
Thats a little bit of Sonnen being Sonnen. When Rich was Champ, Sonnen lost his UFC debut. Then went 1-1 at MW. He was never in a position to challenge for Franklin's belt.
Rich isn't a with a camp and hasn't been for awhile. I believe he works his striking with Phil Nurse and has some other coaches. An elite camp is something thats been missing from his training for a long time now.