LAS VEGAS -- Devin Haney retained his undisputed lightweight championship with a unanimous decision over Vasiliy Lomachenko on Saturday in a fast-paced fight before a sold-out crowd at MGM Grand Garden Arena.

Haney (30-0, 15 KOs), who controlled the first half of the fight with his excellent body work and one of boxing's best jabs, prevailed by scores of 116-112, 115-113 and 115-113. However, Lomachenko closed the fight strong with his trademark flurries from uncanny angles, leading to boisterous boos after the verdict was rendered.

Lomachenko (17-3, 11 KOs) has accomplished so much in his illustrious career: two Olympic gold medals, titles in three divisions and recognition as the best pound-for-pound fighter in the world. But he never achieved his long-held dream of capturing an undisputed championship, and he seemed to indicate that he believed it was stolen from him.

"I don't want to talk about the decision, all [the] people see what happened here today," said Lomachenko, who cried in his locker room afterward before a towel was thrown over his head.

Egas Klimas, Lomachenko's manager, wasn't as subtle, calling the decision a "robbery" and vowing to file an appeal.

"We're not going to let this go," Klimas said. "I guarantee we're going to protest. I guarantee we're going to appeal that decision, because somebody needs to end this injustice."

It has been an emotional journey for Lomachenko, 35, who remained in war-torn Ukraine last year rather than proceed with a deal in place to challenge George Kambosos for the undisputed lightweight championship in Australia. That opened the door for Haney, who quickly accepted the same terms and defeated Kambosos in June to gain all four 135-pound titles.

Haney, 24, defeated Kambosos in Australia in the October rematch, too, and then quickly called out the man he wanted to fight all along: Lomachenko.

At Friday's ceremonial weigh-in, Haney launched Lomachenko with a shove, an act for which he'll be fined from his $4 million guaranteed purse, sources told ESPN. The shove injected plenty of bad blood into a promotion that lacked animosity.

Lomachenko vowed to make Haney pay, and he was able to stun Haney on several occasions with stinging shots delivered from varying angles. But Lomachenko, a typically slow starter, was in a hole after Haney won four of the first six rounds on two scorecards. Lomachenko was able to close strong and won two of the final four rounds on two cards, but what puzzled him was how judge Dave Moretti scored Round 10.

Lomachenko, who earned $3 million, blasted Haney with swarming combinations in the 10th, but Moretti scored it for the champ.

"Maybe I don't understand boxing," Lomachenko joked.

But Haney closed stronger, using his rangy jab and right hands to the body to sweep the final round. It proved to be the difference between a draw and a victory.

"Lomachenko is a future Hall of Famer," said Haney, who is now a free agent after his three-fight deal with Top Rank expired. "He was my toughest opponent by far. He is very crafty, and we put on a great fight for the fans. ... He turns it up in the championship rounds. I just have to take my hat off to him."

Haney said attacking the body was one of the keys to victory.

"The body work won me the fight, so I knew I had to invest in that body," he said. "We watched a lot of tape on Loma, he wasn't the biggest fan of body shots, so we stuck to the game plan, breaking him down."

Haney added: "He would have some good moments during the round, but he wasn't finishing the whole round strong because we invested in the body."

The bout between boxing's two best lightweights and two of the sport's top pound-for-pound fighters was competed at the highest level, entertained the fans and left them clamoring for more because of the nature of the decision. A rematch seems like a natural, but it's far from a formality.

"I've been at 135 [pounds] for a long, long time," said Haney, ESPN's No. 10 pound-for-pound boxer. "This is my 30th fight. I've been here at 135 since I was 16 years old. We're going to go back to the lab and figure out what's next."

What could lie ahead for Haney is a move to 140 pounds and a potential bout against the winner of the June 10 title fight between Josh Taylor and Teofimo Lopez. Haney said before the fight he would remain at lightweight for only one more fight, potentially, if it was against Gervonta Davis or Shakur Stevenson.

Stevenson was ringside and said afterward that he believed the judges delivered the wrong decision.

"Lomachenko should be undisputed champion -- he won that fight," said Stevenson, ESPN's No. 9 pound-for-pound boxer. "He landed the cleaner punches. He pushed the pace."

But it's Haney who remains at home in Las Vegas with all the titles and moves onto bigger and better fights. Lomachenko, too, was a winner in many ways. An underdog heading into the fight after his flat performance against Jamaine Ortiz in October, Lomachenko reminded everyone of his greatness and proved that he's still an elite fighter.

There are still plenty of great matchups for Lomachenko in the star-studded lightweight division even if a rematch with Haney doesn't materialize.

The two fighters put together a bout that will be discussed for years, a rare PPV boxing match that exceeded the expectations and delivered a thrilling, evenly competed fight at the highest level.