Huge assumption here. The only way you get a low first rounder is if a team with a low first round pick signs him. Seeing as how SanFran was the team interested in him, they would have had to give up a high first rounder. Maybe that would be something they wouldn't want to do. So maybe they don't sign Clements. So maybe he stays on the team last year, sucks it up and plays remarkably average because he's pissed, tells other FAs don't sign with Buffalo because we have no Applebees, walks this year, and here we are today talking about how the front office failed because they didn't sign a long-term contract with a player that made it pretty clear that he wanted out of Buffalo.
Furthermore, plenty of teams franchise big name players only to have those players stay. How often does a franchised player actually switch teams. Sure it happens, but (without looking it up), I'm willing to bet that the majority of the time a player is franchised, he plays for that team. To sign a franchised player, you have to pay lots of money and draft picks. It seems like a high price. Hence, Moss is still in NE, Briggs stayed in Chicago, Haynesworth is a Titan, and so on.
I find all this talk of CBs interesting. Exactly what big hole did losing Clements create? Greer stepped in and did well enough. CB play was far from the weakest link on defense. So, until we use the #11 pick on a CB, can we all step back, take a breath and talk about the real needs on the team.