Rob Gronkowski has been acting a bit strangely this offseason. Well, more strangely than the typical level of Gronk strangeness we expect from the NFL’s most prominent goofball.

In his press conference after the Super Bowl, Gronk wouldn’t commit to playing in 2018. Retirement rumors started up almost immediately after that, fueled by Gronkowski’s own cryptic tweets and a joke—and this is Peak Gronk in the cringiest way—that he could leave the NFL to play for the “69ers.” Then he landed a role in a Mel Gibson movie and received interest from the WWE. He acquired a stake in a race horse and held a press conference about dirt biking. All the while, he remained noncommittal about football.

What’s with the big song and dance? In April, The Athletic’s Jeff Howe reported that Gronkowski wants more money, per a source, and that the Patriots don’t expect the tight end to retire. That report puts the offseason into perspective: Gronk’s public persona requires him to be a lovable bro, but a millionaire holding out for a big payday could put a dent in that reputation. Hence, he has to “consider retirement” to negotiate while saving face publicly. But that report also makes sense for another reason: Gronkowski may just be the most underpaid non-rookie-contract player in all of football.

In 2012, Gronkowski signed a six-year extension worth up to $54 million, with $18.17 million guaranteed. That was a sweet chunk of change for Gronk in the moment—it was the richest contract ever handed to a tight end—but he sacrificed a huge amount of long-term flexibility. The extension didn’t kick in until 2014, meaning that the six-year extension essentially tied Gronk to the Patriots through 2019, or for the next eight (!) seasons.

That deal looks worse and worse for Gronk with each passing year. In 2012, the NFL’s salary cap was set at $120.6 million. This year, it’s at $177.2 million—a 46.9 percent increase in just six years. Yet Gronk can’t take advantage of that cap explosion because he’s still locked into his deal for two more seasons. By average value remaining on his deal, Gronk is now the fourth-highest paid tight end at $9 million per year, even though, production-wise, he’s head and shoulders above every other tight end in the league.

Now the Patriots and Gronkowski are working on “tweaking” the tight end’s deal, per the Boston Herald. Last year, the Patriots restructured Gronk’s contract, offering incentives that eventually paid him just over $10 million for last season. It’s likely the “tweaking” being considered this year is something similar.

Whatever extra money the Patriots can get Gronk, he’ll have earned. Gronkowski has averaged 70.4 receiving yards per game for his career. That’s the most by a tight end in NFL history, and it isn’t even close—Hall of Famer Kellen Winslow is second with 61.8 yards per game. Gronk has been so good that it doesn’t make sense to compare him only to tight ends: as far as active pass catchers go, Gronk ranks 14th in receiving yards per game. In total receiving touchdowns, Gronk is fourth among active players, and he’s played in 70-plus fewer games than any of the three players (Antonio Gates, Larry Fitzgerald, and Brandon Marshall) above him.

But we shouldn’t let the numbers do all the talking. What’s the point of writing about Gronk if I’m not going to throw in some highlights? Just look at this:

That’s the most jaw-dropping version of an end zone play that is nearly unstoppable for Gronk. He catches about a handful of these throws per year. Here he is in that corner of the end zone in the Super Bowl:

Gronkowski catches a touchdown off the fade route #SuperBowl pic.twitter.com/NHlY79A3j2 — FlurrySports (@FlurrySports) February 5, 2018

Gronk is what you would get if Groot decided he wanted to play football. His size, catch radius, and speed allow him to turn the middle of the field into a vertical game. As Bill Belichick said after the Patriots beat the Steelers in December, “Even when Rob is covered, he’s still open.” Oh, and he can block, too:

The Patriots offense relies heavily on Gronk and that will continue to be true in 2018, as New England traded away Brandin Cooks and let Danny Amendola walk to Miami. Yet, Gronk isn’t paid like a game-breaking player. By cash earnings, Gronk’s $8.9 million would rank just 17th among wide receivers in 2018, sandwiching him in between L.A.’s Robert Woods and Seattle’s Doug Baldwin. By average value he’d be just 21st, between Pierre Garcon and Marqise Lee.

Just look at what some wideouts got this offseason: Sammy Watkins has never had more yards in any of his four seasons than Gronk had last year, and Watkins signed a three-year deal worth up to $48 million, with $30 million guaranteed. Jarvis Landry is a slot receiver who didn’t crack 1,000 yards last year, and he got a five-year deal worth a maximum of $75.5 million and $47 million guaranteed from the Browns. Allen Robinson missed almost all of last year with an ACL tear and got a three-year, $42 million deal with $25.2 million guaranteed from the Bears.

Of course, any discussion of Gronkowski’s value has to include his lengthy injury history. He’s missed 25 games due to injury over the past six seasons, with a list of maladies so long it isn’t really worth going over every one. He’s had multiple back surgeries, been in the concussion protocol twice, and seen his knees blown out three times. He probably doesn’t wear that arm brace just to look cool. (Seriously, Gronk, you might want to give retirement some more consideration.) Still, when Gronk’s healthy, he’s one of the five or 10 most dominant skill position players in football. But he’ll never get paid that way, because he’s a tight end.

Even if Gronkowski were a free agent this year, the cloud of the franchise tag would hang over any contract negotiation. Since the tag is set by position, the Pats could put it on Gronkowski and give him a one-year deal worth $10.8 million. That’s roughly what Gronk will get paid this year after New England “tweaks” his incentives. If the Patriots tagged him for a second year in a row, that figure would climb to $12.96 million—still a far cry from what top wideouts are earning. And, as we learned from Jimmy Graham’s 2014 dispute, there is virtually no chance Gronk would be considered anything other than a tight end for franchise-tag purposes.

Given his injury history, Gronk will never get Mike Evans money (five years, $82.5 million, $55 million guaranteed), but on an open market some team would surely pay him like a top-10 skill position player. But because of his 2012 contract extension and his position, he’ll almost certainly never make it to unrestricted free agency. The best he can do is mull retirement in the offseason to eke another million or two out of his current deal. If he really plays hardball, the Pats can wait out the next two years on his deal and slap the franchise tag on him in 2020. It’d likely be worth it to pay the premium and tag him again in 2021. By 2022, what will a 33-year-old Gronk be worth?

The Patriots currently have about $14 million in cap space, so there’s potential there to give Gronkowski a well-deserved bonus via a front-loaded deal. But with Gronk still under contract, New England doesn’t have to give him anything. If he gets a few million in incentives this year, which feels likely, he’ll probably go through the same retirement consideration next offseason. But with so little leverage, it’s difficult to see him turning his flirtations with WWE and Hollywood into a significant raise.