The New England Patriots entered last weekend with just $651,000 in cap space, the lowest amount of any NFL team.

So, how the heck were they able to sign a former NFL MVP?

It's a fair question after New England reportedly inked free-agent quarterback Cam Newton to a one-year contract Sunday. We discovered more details on Newton's deal Wednesday, per reports: He has a base salary of $1.05 million ($550,000 of which is guaranteed) with incentives that can bring his earnings up to $7.5 million.

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According to salary cap expert Miguel Benzan, the Patriots have $263,489 in available cap space following Newton's signing. If you're wondering how Newton's deal cost New England less than $400,000 in cap space, Benzan would like to refer you to the "Rule of 51."

The "Rule of 51" in the NFL's collective bargaining agreement is pretty straightforward: During the offseason, only the players with the 51 largest cap hits for the season are counted toward the salary cap.

Newton's deal -- which carries a $1.14 million cap hit, per Benzan -- bumps practice squad defensive lineman Tashawn Bower out of the top 51, meaning his $750,000 deal currently doesn't count against the cap.

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So, the Patriots effectively replaced Bower's contract with that of Newton, a difference of just under $400,000.

The "Rule of 51" only applies to the offseason, so Bill Belichick may have to do more maneuvering before the regular season begins. But as Benzan recently pointed out, Newton's incentives could be classified as "not likely to be earned," which means they wouldn't count against New England's 2020 salary cap even if he reaches them.

In any case, it's remarkable (or "disgusting," if you ask Richard Sherman) that New England was able to land a three-time Pro Bowl QB like Newton for such a discount.

The 31-year-old was hampered by shoulder and foot injuries over the last two seasons, though, which apparently scared other teams away before the Patriots swooped in Sunday.