Even if he was 100% healthy you would still need to retain 50% to get even a so-so return. Given his type of game (never on of speed), 2 back surgeries a couple of knees and the fact that he has logged heavy, hard minutes since he was 18, at best you will be lucky to 3 good years. Even if he did not have the second back surgeries, which occurred after the extension, this was CF's worse contract and second worse move (behind the Ellis trade).
All of the hopefuls will use the one or two positive examples like Kopitar, I offer all of the buy-outs the last several seasons. If you look at them too much term for older players. They should have traded him 2-3 years ago. You could see it coming, but flyers refused to plan for the future and acknowledge the rebuild.