Tim Sylvia was one of the men whose name came up as an opponent for Daniel Cormier in Cormier's final Strikeforce bout. That whole situation seemed to go south fairly quickly and one former UFC champion was replaced by another former UFC champion when it was announced that it would be Frank Mir, not Sylvia, getting the shot at Cormier.
Tim went on the MMA Hour and discussed the situation(transcription via MMA Mania):
I think the UFC might have got ahead of themselves and they really couldn't find anybody to fight Cormier, so, they had asked us and we agreed to it and I think after we agreed to it, they were able to talk Frank into doing it and they probably thought Frank was a better fit for it than myself. I think they'd like to see Daniel win and I think he beats Frank, but he would lose to me. I don't know that he (Frank) is an easier fight than (me) but, he is still in the limelight, he is still in the UFC . Frank is definitely better on the ground than I am, but I think my takedown defense and my striking ability would make a tougher fight for DC definitely. But, he is definitely a rising star right now and he would be difficult for anybody really.
Let's get it out of the way immediately. Tim is out of his mind if he thinks he's a harder fight for anyone than Frank Mir.
Tim is on a three fight win streak over guys who are basically just live bodies. Before that streak started, he lost in half a minute to Abe Wagner. So no, it's not that he's just too dangerous of a fight for Daniel Cormier, the guy who thoroughly beat Josh Barnett in his last fight.