The Patriots aren’t done exploiting every nook and cranny of the rule book just because Bill Belichick is gone.

After New England parted ways with their legendary head coach following a 24-year tenure in which the franchise won six Super Bowls and reached three more, they have already finalized their succession plan, tapping former linebackers coach Jerod Mayo for the job.

As Ian Rapoport explained on NFL Network’s “Good Morning Football” on Friday, Mayo already had a clause written into his previous assistant-coaching contract.

“In Jerod Mayo’s contract that he signed last season … he was designated as the successor to Bill Belichick,” Rapoport said.

“What that means is that when Bill Belichick has been moved aside … Jerod Mayo would take over … Outside, a lot of the speculation focused on Mike Vrabel coming back to New England … Inside the building, especially with owner Robert Kraft, this was always the choice. When he was a player here and I was covering him, we called him Jerod Belichick, just because of how much of a disciple he was for Bill Belichick.

“They kept him in the building, he turned down several head coach interviews, just to stay was the plan. This was written into his contract that he would succeed Bill Belichick.”

At 37 years old, Mayo becomes the NFL’s youngest head coach — he was born a month after Sean McVay, who had previously held that title since the Rams hired him in 2017.

Mayo also played linebacker for the Pats from 2008-15.

While the succession clause deployed by the Patriots is obscure, it is not unprecedented.

As Rapoport noted on Thursday night, the Colts utilized this contract language when Jim Caldwell succeeded Tony Dungy in 2002, and the Seahawks did as well when Jim Mora succeeded Mike Holmgren in 2002.

More recently, the Ravens used this succession plan with general manager Eric DeCosta taking over for his long-time former boss Ozzie Newsome.