Pound-for-pound king Vasiliy Lomachenko will defend his unified lightweight world title against mandatory challenger Anthony Crolla on April 12 at the Staples Center in Los Angeles after their camps made a deal Tuesday night.

The deal for the fight, which will headline a Top Rank Boxing on ESPN+ card to coincide with the one-year anniversary of the launch of the network's streaming service, was made between Lomachenko promoter Top Rank and Crolla promoter Eddie Hearn of Matchroom Boxing one day before the promotional rights for the bout were set to be auctioned off at a purse bid at WBA headquarters in Panama City, Panama.

Top Rank vice president Carl Moretti said the card also will include the light heavyweight debut of super middleweight world titlist Gilberto "Zurdo" Ramirez.

"We thought Loma would be fighting Richard Commey, but because of his hand surgery, a small procedure on a ligament, the focus obviously moved to Loma fulfilling his mandatory against Crolla once that happened. We'll look to unify the titles with Commey afterward, in the late summer," Moretti told ESPN on Tuesday night, shortly after the deal with Crolla was made.

The Lomachenko-Crolla deal is not signed, but all the terms are agreed to and the paperwork is being drawn up, Moretti said.

"Loma wants all the titles at lightweight, and he wants to keep them and defend them," Moretti said.

Commey injured his right hand during his second-round knockout of Isa Chaniev to win a vacant 135-pound belt on Feb. 2 in Frisco, Texas, on the Eleider Alvarez-Sergey Kovalev II undercard. Commey and Chaniev each had previously signed to fight Lomachenko to unify their three belts pending a victory. Commey won but suffered the injury that would sideline him for at least six weeks, making him unavailable for April 12.

That put the focus on Crolla, who became one of Jorge Linares' mandatory challengers when Crolla won a unanimous decision over Daud Yordan on Nov. 10 in Crolla's hometown of Manchester, England.

Now Crolla, a heavy underdog, is headed for his first fight in the United States and only his second outside of the United Kingdom; he fought in Germany in 2008.

"It's a huge opportunity for Anthony Crolla," Hearn said. "He has earned his stripes, a former world champ who has fought the best. He won the final eliminator against Yordan in November, and I'm happy he gets this chance now. Lomachenko is a great talent, but Anthony is in great shape and ready for this chance."

In November 2015, Crolla (34-6-3, 13 KOs) won a lightweight world title by fifth-round knockout from Darleys Perez in Manchester in an immediate rematch of a draw four months earlier.

Crolla, 32, defended the title with a seventh-round knockout of Ismael Barroso, then lost it by decision to Linares in September 2016. Linares outpointed Crolla in an immediate rematch in March 2017, after which Crolla reeled off three wins in a row to earn the title shot against Lomachenko.

Lomachenko (12-1, 9 KOs), who turned 31 on Sunday, has won world titles in three weight classes. He moved up to lightweight and knocked out Linares in the 10th round in May to win a world title in his third division. On Dec. 8, Lomachenko, a two-time Olympic gold medalist from Ukraine, dropped Jose Pedraza twice in the 11th round en route to a unanimous decision victory to unify two belts.

Ramirez (39-0, 25 KOs), 27, a southpaw from Mexico, will face an opponent to be determined in the co-feature. He won a super middleweight world title by shutout decision of Arthur Abraham in 2016, and he has made five defenses; but Ramirez told ESPN earlier this month that making 168 pounds was becoming increasingly difficult and that he would move up to light heavyweight for his next bout.

Ramirez's aim is to get acclimated to the division and put himself in the title picture in a talent-rich division that Top Rank is heavily involved in as the promoter for world champion Oleksandr Gvozdyk and world titlist Artur Beterbiev, and as the co-promoter for world titlist Kovalev and former titleholder Alvarez.