Jonathan Casillas is spending this week preparing for life after football.

The linebacker has already accepted that his playing future likely won't be with the Giants.

The combination of a new coaching staff and mitigating factors stemming from age and the physical wear and tear that comes with a nine-year NFL career has Casillas believing he will probably be headed elsewhere via free agency.

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“I've spoken to (the Giants) briefly. I didn't have a formal conversation with them about any contract or getting me back there or anything like that," Casillas told co-host Bill Polian and me Monday night on SiriusXM NFL Radio. "It doesn't seem like they love me as much as the old staff did."

After a Super Bowl-winning season with the Patriots, Casillas signed a three-year, $8 million contract with New York in 2015 when Tom Coughlin was the head coach and Steve Spagnuolo was the defensive coordinator. Casillas amassed 184 tackles in 31 games (22 starts) in his first two seasons and was elected a captain by his teammates.

Casillas started the first eight games for the 2017 Giants before landing on injured reserve with neck and wrist injuries.

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He admits the latter ailment, as well as the fact he turns 31 in June, could be bigger deterrents for the Giants than how he would fit in new defensive coordinator James Bettcher’s system.

“If they don’t think I can do it, I don’t think it has anything to do with what I used to do,” said Casillas, who has played all linebacker spots in multiple defensive schemes during a career that also includes stints with Saints (2009-12) and Buccaneers (2013-14). "It's more about what they think I’m going to do now in my 10th year (and) coming off a neck injury. That’s a daunting thing to some teams.

"But I've been around enough to understand the game. I might not be as hot a commodity as I used to be. But whoever gets me, if it’s somebody else and not the Giants, they're going to get a great player and a great leader in the locker room."

Not to mention one who already has started trying to make post-NFL career plans. To that end, Casillas is one of 25 current and former players partaking in the third annual NFL Business Academy at the University of Michigan.

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“I'm preparing myself to not play football ever again," Casillas said. "I still know I can play football and want to be in New York. I'm a (New) Jersey boy.

"I definitely want to be home, but at this point it's not really up to me."

The NFL free-agent signing period begins March 14.

Alex Marvez can be heard from 7-10 p.m. ET Tuesday and 8-11 a.m. ET Wednesday through Friday on SiriusXM NFL Radio.