By Michael Donovan

If Eagles Nation was stunned by Fletcher Cox’s record-breaking contract, check out how Cox, the Birds’ gem of a defensive tackle, reacted.

When his agent Todd France told him that he had agreed to a six-year, $103-million contract:

“It’s really mind-blowing,” Cox said yesterday in a presser at NovaCare.

Cox had returned to town to sign the contract, which includes more guaranteed money than any non-quarterback contract in NFL history.

“Dealing with that much money is really mind-blowing. I’m really excited about it.”

Cox said his first call was to his mother. His goal now is to make sure that “mind-blowing” amount of money doesn’t change him, as a person or as a player.

“I look at it as I just have to continue to humble myself,” Cox said. “Just keep working every day in practice and being the leader that this team is expecting me to be.”

The deal comes as Cox prepares to play in new defensive coordinator Jim Schwartz’s aggressive 4-3 scheme. After three years as a defensive end in a 3-4, two-gapping scheme, Cox will be freed up to attack gaps and make plays.

“You can expect me to be in the quarterback’s face a lot,” said Cox, who had 9.5 sacks last season and was selected for his first Pro Bowl.

“The way the scheme is, right off the football and getting after the quarterback, that will help a whole lot.”

Howie Roseman, the Eagles’ executive vice president of football operations, said the team’s emphasis this offseason was on locking up its best young players. Cox, the team’s first-round draft choice in 2012, was at the top of that list.

“He’s a great player,” Roseman said. “He’s someone that we can build around, on and off the field. We’re never letting him leave the building. These [contractual years] are all his prime years. It’s hard to find players who can change the game on either side of the ball and then represent what you are about.

“He’s got a chance to be a great player in the history of this franchise. Our responsibility is keeping as many great players as we can.”

Cox said he believes his best football is still ahead of him.

“I’ve got a ways to grow, man,” Cox said. “I don’t think I’ve hit that ceiling yet.”