I'd give him near minimum salary with bonuses if he meets certain incentives. If he is still a workhorse and stays healthy, he is compensated. Otherwise he makes close to minimum and rides the pine.
In the NFL, you cannot afford to pay players based upon past performances. That is how teams get into cap problems. You pay for the here and now. If a top player's skills drop off, so does their pay. It may be hard to swallow, but that is they way of the business.