The Buccaneers added one future Hall of Famer this offseason when they signed away Tom Brady from the Patriots. On Tuesday, they made a stunning move to add another, as the rights to retired tight end Rob Gronkowski were traded with a seventh-round pick to Tampa Bay for a fourth-round selection. Gronk is coming out of retirement to join up with his favorite quarterback for another ride. This one's just on a pirate ship.

Let's grade this deal and get a sense of what Gronkowski might do with the Buccaneers after a year of rest:

New England Patriots get: 2020 fourth-round pick (No. 139)

Tampa Bay Buccaneers get: TE Rob Gronkowski, 2020 seventh-round pick (No. 241)

Patriots grade: C

Buccaneers grade: B+

Why the Patriots got only a fourth-round pick

Why did it cost the Buccaneers only a fourth-rounder to acquire arguably the greatest tight end in football history when the Falcons sent a second-round pick to the Ravens for Hayden Hurst and the Steelers sent a fourth-round pick to the 49ers for Vance McDonald? Bill Belichick almost never misses a chance to extract maximum value in a trade; he suddenly let Gronk leave at a discount out of the kindness of his heart?

The reality is that trades are about leverage, and the Patriots didn't have any. They desperately could have used Gronkowski as a weapon for Jarrett Stidham, Brian Hoyer or whomever else is going to play quarterback in 2020. It's clear Gronk didn't want to be there and probably would have simply stayed retired if New England hadn't facilitated a trade.

If Gronkowski had pushed his way back onto the active roster, the Patriots would have been in an immediate financial bind. They have just $2.1 million in cap space, and he has $10 million due in the final year of his deal. Guard Joe Thuney's $14.7 million franchise tag became fully guaranteed when he signed it in March, so the Pats couldn't have created room by letting the offensive lineman leave.

Realistically, the Pats don't have much cap flexibility thanks to the $24 million in dead money they owe in 2020, so it would have taken something like a new contract for cornerback Stephon Gilmore to create immediate, short-term cap space. Even if they do create that space, it's probably more valuable for them to use it on a veteran quarterback such as Andy Dalton or Cam Newton.

With Gronk wanting to play alongside only Brady, the Pats had just one team with which to negotiate. The Buccaneers were able to point toward similar deals from the past, such as when the Raiders sent a fifth-round pick to the Seahawks for a sixth-round pick and the rights to the retired Marshawn Lynch. Teams have not typically treated retired players or coaches as valuable propositions, in part because those players and coaches intend to stay retired unless they get traded to the team of their choosing. The same thing seems to be true here.

What about the Bucs' other tight ends?

The next question I had after I saw the trade compensation was wondering why O.J. Howard wasn't included. After all, the Patriots still desperately need tight end help, and Howard has a base salary of only $2 million in the final year of his rookie deal to go with a possible fifth-year option at $9.2 million in 2021. He spent much of 2019 in Bruce Arians' doghouse, and with Gronk joining Howard and Cameron Brate in the tight end room, it seems as if the 25-year-old former Alabama star would be on his way out of town.

If anything, though, the odd man out in this trio could be Brate. For one, even though Howard didn't have the sort of receiving workload we would have expected, he played far more frequently than Brate. Howard lined up for 745 snaps despite missing two games, and Brate was on the field for 408 snaps across 16 games. Brate also ran pass routes on more than 83% of his snaps. Howard went out on a pass route just over 36% of the time. If the Bucs intend to use Gronkowski primarily as a receiving weapon, it makes sense for him to replace Brate in the lineup, not Howard.

Rob Gronkowski sat out all of last season, but he caught 47 passes for 682 yards and three touchdowns over 13 games in 2018. Jim Rogash/Getty Images

The Bucs also are operating under financial constraints. They have about $3.6 million in cap room after absorbing the final year of Gronk's deal and should still be in the veteran market for help at running back, right tackle, defensive tackle and possible depth in the secondary. They'll address some concerns in the 2020 NFL draft, of course, but vets are going to want to play with Brady. Howard is still relatively cheap, as mentioned, but Brate has a base salary of $4.3 million, which is double what Howard would cost via trade. If Brate was the only tight end the Bucs were offering, the Patriots might not have been interested at that price.

Gronkowski can play whatever role the Buccaneers want when healthy, so at the end of the day, they can deal either of their tight ends and play the other with Gronkowski when they want to work out of 12 personnel. They should be able to get something in this compensation range back in return, which would mean they upgraded from Jameis Winston and Brate or Howard to Brady and Gronkowski for nothing more than money. That's the sort of magic we used to see the Patriots pull off.

What's left in the Gronk tank?

The last time we saw Gronkowski on a football field was in Super Bowl LIII, when his catch set up the only touchdown in a 13-3 Patriots victory over the Rams. The 2018 season was difficult for the star tight end, with a clearly hobbled Gronk missing time and failing to serve as the red zone destroyer we knew from years past. He averaged 52.5 receiving yards per game -- his lowest average since 2010 -- and scored only three touchdowns. We did see a resurgence from him as a receiver in the postseason, during which he caught six passes for 79 yards in the AFC Championship Game win over the Chiefs and six catches for 87 yards in the Super Bowl.

Even if Gronkowski didn't rack up a ton of touchdowns in his final season, he was still an effective receiver. He finished sixth in Football Outsiders' DYAR statistic, which measures performance against replacement level and adjusts for game situation. The Patriots seemed to spend 2018 doing their best to conserve his legs for the postseason. He ran routes less frequently than he had since 2012. They turned to him in moments and on drives when they needed big plays. While the Dolphins revealed that Gronkowski was probably not cut out to play safety on the laterals play they used to beat the Pats during the regular season, he was typically able to answer the call when the Patriots needed those big plays.

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In Tampa, for whatever Gronkowski offers as a receiver, he could actually be more valuable to the Bucs as a blocker. The 30-year-old retired as arguably the league's best blocking tight end independent of his receiving skills, and the Pats' running game was a mess in 2019 after losing his ability to manhandle defensive linemen at the point of attack. With right tackle as the most significant weakness on the Tampa roster, adding Gronk means Arians can support that tackle with a dominant blocking tight end. The Bucs probably don't want Brady to throw the ball 626 times in 2020, which was Winston's league-leading total in 2019. Adding Gronkowski as a blocker should make it easier to run the football.

When they get into two-tight end sets, the idea of Gronkowski and Howard as blockers would give the Bucs the sort of run/pass mismatch the 49ers thrived on last season and the Patriots used to infuriate defensive coordinators in years past. Come out in your base defense and the Bucs can split out Chris Godwin, Gronkowski and Howard against your linebackers and safeties. Come out in a nickel or dime package and you get Gronkowski and Howard blocking defensive backs in the run game.

All of that depends on Gronkowski being healthy enough to play, though, and those concerns aren't going away. He missed an average of just over four games per season during his last seven NFL campaigns. There's a chance he plays 16 games, of course, but it's more realistic to project him to play something closer to 12 to 14 games on average, with the realistic possibility of a more serious incident costing him the majority of the season.

In addition to a multiligament knee injury and the normal wear and tear that physical tight ends deal with, Gronkowski suffered a serious back injury in college that already has led (directly or indirectly) to back surgeries in 2009, 2013 and 2016. He was reportedly concerned he might need a fourth back surgery in 2018, which led to thoughts about retirement. I'm sure a year of rest and reduced weight has helped his back, but we have already heard he is putting on weight to get back into football shape, and one year of rest isn't going to solve a decade of back issues.

I can point to one person who thought it was time to move on from Gronkowski before the 2018 season, and his opinion is usually pretty insightful. In April 2018, Belichick agreed to send Gronkowski to the Lions for a first-round pick and a swap of second-rounders. Gronkowski was able to effectively veto the deal by threatening to retire. While that deal was obviously for much better compensation, Belichick was clearly willing to move on from Gronkowski just before his receiving production dropped off in 2018. In general, when Belichick has decided to move on from one of his star veterans as they approach or pass 30, he hasn't regretted that choice.

That was with Brady, of course, and Belichick no longer has the star quarterback to make players who struggled elsewhere excel with the Patriots and vice versa. As recently as last season, players wanted to leave their dysfunctional organizations to win in New England. Now, we're seeing one of the best players in Patriots history tread that path in the opposite direction.