This.
CJ has been in the league for several years, and has never even slightly improved at pass blocking. While it's not the #1 responsibility of a RB in the league, it's still an important one, and CJ is just not very good at all at blocking.
One of the worst plays of this past season, don't remember who it was against but it was later in the season: CJ blew a block on a pass-rushing defender, who came free at Orton but managed to miss him and fall to the ground. Orton danced around long enough for the defender to get back up and sack him from behind. After missing his block on the defender, CJ merely stood around and watched the defender get back up and make the play. Didn't even make a half-hearted attempt to stop him.
I lost any remaining desire to keep CJ on the team at that point. He can be a home run hitter, but he has no interest or ability to become even average at his other responsibilities.