FOXBOROUGH, Mass. — Billy Big Bucks! What has gotten into you?

New England Patriots coach Bill Belichick was uncharacteristically active Monday, the first day he could negotiate with free agents from other teams.

Between reported contract agreements with Tennessee Titans tight end Jonnu Smith, Baltimore Ravens outside linebacker Matthew Judon, Miami Dolphins defensive tackle Davon Godchaux and Philadelphia Eagles defensive back Jalen Mills, Belichick shelled out $81 million in bonuses and guarantees. And that was before he locked up wide receivers Nelson Agholor and Kendrick Bourne and defensive tackle Henry Anderson later in the day.

In a reflection of how out of character it is, consider this: The Patriots spent $51 million in bonuses and guarantees on free agents over the prior three offseasons combined.

As for the sudden change, there are a couple different ways to look at it.

Could it be Belichick is so motivated by watching quarterback Tom Brady depart and win a Super Bowl in his first season with the Tampa Bay Buccaneers that Belichick has officially kicked off a 2021 Vengeance Tour?

That’s a fun one and perhaps there is some competitive fire there, but it doesn’t seem to hit the bull’s-eye.

Another thought: Belichick is a bottom-liner and simply assessed the roster that produced a 7-9 season — with the Patriots missing the playoffs for the first time in 12 years — and realized it wasn’t very good. So as much as he would prefer to draft, develop and re-sign players, especially at tight end and wide receiver to help an offense that ranked 30th in passing yards per game, that wasn’t an option. Same with defensive tackle to help a shaky run defense.

This also makes a lot of sense but, still, doesn’t completely tell the story.

What has most directly sparked such an aggressive approach, according to those familiar with the thinking, is the view the 2021 offseason was a rare opportunity based on the NFL’s plummeting salary cap.

Remember, the cap dropped to $182.5 million this year. It was $198.2 million in 2020, so this marked the first drop since the collective bargaining agreement of 2011.

Because of that, it thinned the field of teams the Patriots were competing against for free agents because many teams were scrambling just to get under the cap. That sweetened the free-agent pool, making players in the prime years of their career available who might not have otherwise hit the market; consider that Smith and Bourne are 25, Godchaux and Mills are 26, Agholor is 27 and Judon 28.

So with an abundance of salary-cap space to work with, and knowing the cap is going to spike in the coming years because of television broadcast deals, Belichick and the Patriots went all-in like never before.

In the perfect Patriots world, they have capitalized on unprecedented market conditions, dramatically improving the team.

In the worst-case scenario, they have overthought it, strayed too far from their draft-and-develop roots by committing too much to non-homegrown players, and will ultimately pay a similar price that other teams who also “won” free agency in March have in past years.

For now, there’s plenty of optimism at One Patriot Place, where a new parking spot might need to be created for the Brinks truck greeting the team’s additions.

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