According to ESPN's Adam Schefter, the team added $2.5 million in incentives to McCoy's contract based on production.
Per Spotrac, McCoy already had a base salary of $6 million for 2017 with a cap hit of $8.875 million.
Only Pittsburgh Steelers star Le'Veon Bell has a larger cap hit this year among running backs.
Schefter explained the uniqueness of the deal:
Adam Schefter @AdamSchefter
Bills didn't have to add $2.5 million in incentives to LeSean McCoy's deal when it had three years left. Rare deal, good for both sides.2017-9-7 23:26:18
Even at 29 years old, McCoy is coming off one of the best years of his career. He rushed for 1,267 yards to go with 356 receiving yards, totaling 14 touchdowns despite splitting time with Mike Gillislee. Without any established backups this year, he could have even bigger numbers.
New Bills coach Sean McDermott explained Wednesday how big the workload could get for the veteran.
"We play to win, and whatever it takes to win the game, that's what we're going to do," he said, per Mike Rodak of ESPN. "If it means he's got to play every snap, that's what we'll do if he's feeling good, like it is for every player. I'll look him in the eye, say, 'How do you feel? Feel good? OK, let's go.' No different with LeSean."
With new incentives in place, McCoy likely won't be taking himself out of games any time soon.