Terence Crawford was stripped of his IBF title months after he won the 147-pound belt from Errol Spence Jr. in July.
The ninth-round TKO victory crowned Crawford as the undisputed welterweight champion and cemented his place as ESPN's No. 1 pound-for-pound boxer.
Crawford, 36, still owns the WBC, WBA and WBO belts, but Jaron "Boots" Ennis is now the IBF titleholder after he was elevated from interim champion.
Why was Crawford stripped of his title so soon after winning it? What did Ennis accomplish to earn the title? ESPN answers those questions and more:
Why was Crawford stripped by the IBF?
Boxing's four recognized sanctioning bodies (WBC, WBA, IBF and WBO) govern world titles across 17 weight classes.
When a fighter holds one more than one title in a weight class -- such as Crawford, Canelo Alvarez or heavyweight champion Oleksandr Usyk, among others, there's a rotation system to decide which mandatory defense is due next.
There are also optional defenses that the four sanctioning bodies allow along with exceptions to mandatory defenses for unification fights and other major fights in special circumstances.
After Crawford defeated Spence, the IBF didn't allow for even one optional defense. On Aug. 25, the IBF ordered Crawford to begin negotiations with Ennis to be concluded by Sept. 24.
But there was one issue: the Crawford-Spence bout contained a two-way rematch clause that meant the loser of the bout could contractually exercise his right to an immediate rematch.
Even if Crawford wished to fight Ennis rather than take part in a far bigger matchup against someone like Alvarez, he would have to face Spence after the latter exercised the rematch clause in August.
Unlike the other three sanctioning bodies, the IBF doesn't recognize rematch clauses as an exception to a mandatory defense, so Crawford was stripped with the title handed to Ennis.
When was the last time Spence made a mandatory defense?
Somehow, Spence has made only one IBF mandatory defense, a first-round KO of fringe contender Carlos Ocampo in June 2018.
How Ocampo inherited that position in the first place is a mystery, par for the course when it comes to boxing's sanctioning-body shenanigans.
Spence won the IBF title from Kell Brook in May 2017 via 11th-round KO. Since then, he's suffered two serious injuries -- a car accident that hospitalized him for days and a detached retina that scrapped a fight with Manny Pacquiao -- and fought seven times.
Three of those seven fights were unifications (fights against Shawn Porter, Yordenis Ugas and Crawford). The IBF allows such unification bouts against other champions to take precedence over mandatory fights.
Following a mandatory defense, a fighter is typically allowed to make a voluntary defense against someone who is ranked. One such voluntary defense took place against Mikey Garcia. Another against Lamont Peterson. Danny Garcia was a WBC mandatory defense.
What isn't clear: Why the IBF didn't crown an interim champion until January when Spence dealt with two yearlong-plus layoffs.
"We probably should have ordered an interim earlier given the extent of Spence's injuries," IBF president Daryl Peoples told ESPN on Friday. "We typically try to stay away from interims but concede that it should have been done earlier. We underestimated his recovery time. I have to own that. Nothing nefarious."
What did "Boots" Ennis accomplish to earn the title?
Ennis (31-0, 28 KOs) is undoubtedly one of boxing's fastest-rising stars. The 26-year-old from Philadelphia has impressed with his blend of athleticism, punch variety and power.
What Ennis hasn't been able to do: secure name opponents.
"What's gonna be their excuse now?!" Ennis wrote on Instagram on Thursday, referring to his new status as champion.
Ennis won the interim title in January when he scored a shutout decision over fringe contender Karen Chukhadzhian. Ennis made his first defense in July in his first "Showtime Championship Boxing" main event, a homecoming of sorts in Atlantic City with a 10th-round of Roiman Villa.
Now, Ennis should be lined up for some meaningful fights, even if he's unlikely to ever fight Crawford or Spence, who could meet again at 154 pounds.
The best option for Ennis could come against the winner of a planned bout between Eimantas Stanionis and Keith Thurman next year.
What's going on with the Crawford-Spence rematch?
The winner of the first bout selects the weight for the second bout.
Spence said afterward that he was done fighting at 147 pounds. So, if he wants the rematch at 154, Crawford will have to agree to the change in weight.
Crawford has all the leverage here. He could ask Spence to make financial concessions in exchange for an increase in contracted weight. It's possible the fight doesn't happen at all.
The weight for the return bout hasn't been agreed upon yet, sources said, and nothing has been finalized as PBC seeks new TV deals with longtime broadcast partner Showtime exiting boxing programming at the end of the year.
Now that Crawford is no longer undisputed, how many such champions remain in boxing?
Josh Taylor was the undisputed champion at 140 pounds before he vacated three of his four titles to pursue a rematch with Jack Catterall.
All four titles at junior welterweight are now splintered after Taylor lost his WBO belt to Teofimo Lopez Jr. in June.
Jermell Charlo held all four titles at 154 pounds, but he was stripped by the WBO in September after he moved up to 168 pounds for a fight with Alvarez. Charlo still holds the WBA, WBC and IBF super middleweight titles, while Tim Tszyu is the WBO champion at 154.
That leaves Alvarez as boxing's lone men's undisputed champion. Naoya Inoue, who fights Marlon Tapales on Dec. 26 in Tokyo for the undisputed championship at 122 pounds, is likely to join Alvarez.
There are five undisputed champions on the women's side: Amanda Serrano, Alycia Baumgardner, Katie Taylor, Chantelle Cameron and Claressa Shields.
Devin Haney remains the undisputed champion at lightweight until Thursday, when Shakur Stevenson meets Edwin De Los Santos for the vacant WBC belt at 135 pounds. Haney, meanwhile, moves up to 140 pounds for a Dec. 9 bout with Regis Prograis.
The biggest undisputed title fight of all comes in February when Tyson Fury meets Oleksandr Usyk in Saudi Arabia for all four heavyweight belts.
Wait, won't the same situation play out with Fury, Usyk and the IBF?
That's right -- the winner of Fury-Usyk will almost certainly be stripped of his IBF title.
Fury holds the WBC belt while Usyk will enter the ring with the WBA, WBO and IBF titles. Usyk fulfilled his WBA mandatory obligation in August with a ninth-round KO of Daniel Dubois. Next up in the rotation is the IBF.
Fury-Usyk, like Crawford-Spence, contains a bilateral rematch clause that the loser can exercise to guarantee an immediate return bout.
The IBF informed both parties last month that the winner of Fury-Usyk must make a mandatory defense against Filip Hrgovic with no intervening bouts, and that the organization will not grant exceptions.
"The IBF wrote that if I won my last fight and if Usyk beat Dubois that the IBF would enforce my mandatory status to fight Usyk for the title," Hrgovic told ESPN. "The IBF has now allowed Tyson Fury and Usyk to do a unification first. The winner of that fight is mandated to fight me immediately after with no other intervening fight, so I expect to fight for the heavyweight championship early next year.
"I'm disappointed at the delay, but I will stay ready and I won't let it distract me from my goal of winning the title. Whether against Usyk or Fury, my time is coming."
If Fury or Usyk vacate the IBF title, as it stands right now, Hrgovic would meet Otto Wallin for the belt.