Clark was injured at the beginning of the season, and with the season going sideways, the Broncos decided to try to get rid of some of their more expensive pieces, like Gregory and Clark. I don't think Denver's assessment means that much--they haven't been a good evaluator of talent recently.
I think we have Frank Clark under the best of situations. He's under contract only until the end of the year, meaning we can move on and no cap hit next year. He also has maximum incentive to show that he's still the man, and he has 11 games to do that. If he wants to get a decent offer for next year, he's going to have to do it now, and can't wait for the post-season because there's no guarantees there. He also is probably motivated by Sean Payton's remarks that the Broncos have better players than him.