NFL: AFC Divisional Playoff-Los Angeles Chargers at New England Patriots

Rob Gronkowski is shown during warmups before the Patriots-Los Angeles Chargers AFC Divisional playoff game in January of 2019.

Rob Gronkowski couldn't stay retired.

Not with Tom Brady still playing. And especially not with Brady playing for a team not named the Patriots.

According to a source with knowledge of the situation, the all-world tight end has imagined this scenario of reuniting with Brady for quite awhile. This wasn't a spur-of-the-moment decision to request a trade. If Brady ever left, Gronkowski was going to join him wherever he landed.

That was always the plan, according to the source.

But coming out of retirement was predicated on one condition: The Patriots, who still had his rights, had to trade those rights to Tampa Bay. Somewhat shockingly, that came to pass Tuesday.

As the story goes, Gronk wanted in on Brady's new team, and the only person standing in the way of that happening was Bill Belichick.

Gronkowski basically had Belichick over a barrel. If Belichick traded him someplace else, Gronkowski made it known he would stay retired. Returning to the Patriots wasn't an option.

The fun-loving Gronk had his fill of The Hoodie. He wanted a change.

Being with Brady also provides him a chance of winning more Super Bowls. The Patriots are no longer the favorite they were. The Buccaneers, with Brady, are all the rage.

While Gronkowski seemed to be having a great time in retirement, working with Fox during the football season, appearing on "The Masked Singer" and moonlighting for the WWE, the appeal of joining Brady in a loaded Bucs offense was too good to ignore.

Even with the litany of devastating injuries he endured during his nine seasons with the Patriots, and now being pain-free for one of the few times in his adult life, Gronkowski still felt the tug to play football. But only on his terms.

So why would Belichick do Gronk and Brady any favors? Why would he hand over arguably the greatest tight end to have played the game, along with a seventh-round pick, for a paltry fourth rounder?

One might picture Belichick telling Gronk's camp to go fly a kite -- that being a polite version of the response. He'd say something to the effect it would be a cold day in hell before he caved to any player's demand.

Giving in just isn't part of Belichick's playbook. Only the six-time Super Bowl-winning head coach acquiesced and made it happen.

Has he gone soft?

To Belichick, Gronkowski became a useless asset. He also has to be figuring that Gronk, who turns 31 in May, doesn't have much left given he's been mentally checked out for years.

But what if that notion is wrong?

What if a re-energized Gronk returns to being a force, or maybe 80-to-90 percent of what he was? What if Brady and Gronk ride off into the sunset with another championship, this time in Tampa?

Not the best look for Belichick, especially if the Patriots offense struggles this season and beyond.

Heading into the draft, the tight end room in New England doesn't exactly inspire confidence. Nor does the quarterback situation, with Jarrett Stidham and Brian Hoyer the current in-house options.

Gronkowski, however, smartly leveraged his return, and pretty much forced Belichick to comply.

"The day that I retired, within 24 hours there was already rumors that I was coming out of retirement," Gronkowski said Monday on Watch What Happens Live. "I'm feeling good right now. I'm happy where I'm at, and you just never know, man. You just never know. You never know. I'm not totally done; I like to stay in shape, but I've got to get that feeling back."

It came back, and sooner than you'd think.

With Brady acknowledging to Howard Stern on the shock jock's Sirius XM radio show a few weeks back that he sensed his time with the Patriots was nearing an end after negotiations for a multi-year extension went south prior to last season, Gronkowski likely knew the same. With Brady unfettered by a franchise tag, Gronk probably figured Brady was headed for free agency and out the door.

He kept alluding to a return, always leaving the door open. But no one bought in.

There was certainly a buzz in the air, but much of it was chalked up to Gronkowski goofing around, and pulling everyone's leg for attention.

Only, for the boy who cried football, this time was real.