Vasiliy Lomachenko is making a rock-solid case to be regarded as the best boxer in the world, the pound-for-pound crown that can start a thousand arguments. There would be little or no dissent, however, from Anthony Crolla, whom the peerless Ukrainian destroyed inside four rounds in Los Angeles on Friday night and who is now seriously considering retirement. “He’s as good as what they say, a fantastic fighter,” the 32-year-old Mancunian said through swollen lips.

The biggest blow Crolla has taken in his life was a concrete slab thrown at the side of his head by an intruder he chased from a neighbour’s back garden in 2014. “You’ll never box again,” his doctor said that Christmas. He did – and Friday’s fight was the ninth since that night. Was it his last? The left hook in round four, followed by a right to the temple that pitched him face first on to the canvas, looked very much like the full stop to a slow-burning career over 13 years in which the universally admired Mancunian won 34 of 44 bouts, a world title and made some decent money.

“I’ve banged on about staying in boxing too long,” he told Sky Sports. “I love this sport, it’s a big part of my life, but I’ve not got much longer left. I don’t want to go out like that but the end is near.”

It was a challenge beyond his control from the first minute of the fight. Every facet of the champion’s arsenal clicked instantly in front of a capacity crowd at the Staples Center as he calmly and brutally defended his WBA and WBO lightweight titles against a mandated opponent who could not have prepared more diligently.

Crolla discovered quickly what he had suspected, what everybody in boxing knew: Lomachenko is a master of space and timing, pulling him this way and that with feints and sublime footwork. He hits with precision and full force. He is impossibly difficult to measure for a counter. He is, in short, the complete fighter.

As Darren Barker said ringside: “Timing can’t be taught, it comes naturally. And the punch variation was exceptional. That was punch-perfect. He made a real statement there. He’s shown why he’s arguably the No 1 fighter out there. He’s just got it all. I do not seem him getting beaten again.”

Crolla said before the fight: “Lomachenko is a hell of a fighter. I would say he’s the best on the planet at doing what he does. But no man’s invincible.” On Friday night – and many others – he was just that and will remain so until someone even more exceptional emerges.

Vasiliy Lomachenko displays his title belts after retaining his WBA and WBO lightweight titles. Photograph: Damian Dovarganes/AP

The manner of the finish was chilling. After two lopsided rounds there was confusion towards the end of the third when the referee, Jack Reiss (whose 116-113 score in favour of Orlando Salido handed Lomachenko his only defeat in his second paid fight, six years ago) gave Crolla a standing eight count, ruling the ropes had prevented his going down under a barrage of head shots. It only postponed the inevitable.

When they resumed, Crolla, still dazed, was decked face first for a full count by a left hook and a finishing crisp right to the temple. He rose in bloodied confusion, protesting to the ringside doctor: “I’m fine.” He was about as far from “fine” as it is possible to get in a boxing ring.

“No one’s done that to Anthony Crolla,” Spencer Oliver observed.

Lomachenko is so dominant the most credible opponent left for him at lightweight is Mikey Garcia, who lost last time out when he moved up two divisions to welterweight, where Errol Spence Jr outclassed him over 12 rounds last month as completely as he did Kell Brook.

“Mikey Garcia. I dunno,” Lomachenko said in the ring. “I’ll stay at 135 for as long as possible, to unify all the titles.” Garcia still holds the WBC belt and Richard Commey is the IBF champion. Lomachenko would start a strong favourite to beat both of them.

As Crolla’s trainer, Joe Gallagher, remarked beforehand, Lomachenko does not just beat opponents, he embarrasses them. He has mastered all styles of opponent and, in an astonishing run between November 2016 and December 2017 he forced four quality challengers – Nicholas Walters, Jason Sosa, Miguel Marriaga and Guillermo Rigondeaux – to quit. They had only three defeats between them in 88 contests.

Walters, once a feared two-division champion, has not fought in the two years since and, at 32, is a marginal figure; Sosa has lost one and drawn two; Marriaga has won twice against journeymen; Rigondeaux, at 38, knocked out 16-8 trialhorse Giovanni Delgado in his only fight since losing to Lomachenko in December 2017. That is what he does to good fighters. He shortens careers.

Lomachenko is not a big lightweight, having moved up from featherweight to super-feather then 135lbs in a whirlwind 14-fight professional career after a long, glorious reign as the best amateur in boxing. At 31, lightweight looks to be where he will settle for the rest of his fighting days although the lack of credible challengers may tempt him to see what he can do elsewhere. There may even be a catchweight showdown with Manny Pacquiao – and that would bring him face to face with his chief inquisitor, Freddie Roach, reunited with the Pacman after a mysterious split.

The bloodied Anthony Crolla

receives attention after being knocked out by Vasiliy Lomachenko. Photograph: Yong Teck Lim/Getty Images

The former trainer of the year has taken some convincing Lomachenko is the best pound-for-pound fighter in the world. Before Friday’s bout he reckoned two compatriots, Terrence Crawford and Spence, were ahead of the Ukrainian in that category, sayinginsisting: “Lomachenko is beatable.” You could almost hear the Stars and Stripes fluttering in the background.

Roach dislikes what he calls Lomachenko’s “clown behaviour”. But he got it way wrong when he predicted aging genius Rigondeaux would stop him. The excellent Cuban was as demoralised as all the others. Roach also thinks Garcia could beat Lomachenko.

However, after Lomachenko’s demolition of Crolla, Roach softened his criticism. “He looked really good tonight,” he said. “I love when he’s serious like that. When he’s like that he can beat anyone in the world.” And he concedes Lomachenko would beat the rising Honduran knockout star, Teófimo López. “He’s a more complete fighter.”

The rest of the industry seem convinced. Carl Frampton was moved to tweet: “When people get asked who their favourite fighter of all time is? You hear the usual names. Ali, Tyson, Leonard, Hagler, Duran, Chavez etc. Are we allowed to say Lomachenko yet? Cause I think hes mine.”

Crolla has long called himself “Million Dollar”; Lomachenko’s gown is embroidered with “Billionaire Loma”. It pretty much described the gap between Lomachenko and his doomed foe – as well as everyone else.

Right now Loma is invincible.