British light-heavyweight Joshua Buatsi earned a win yet underwhelming debut to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a competitive 10-round contest at the Co-op Live Arena.
But the challenger found success, connecting with powerful individual punches in a fight where the approaches didn't complement each other, with excessive holding disrupting the fight.
Two judges scored it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my greatest showing but how do champions respond? They win," Buatsi commented in the arena as he was greeted with boos from the audience.
The British fighter bounced back after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Various analysts believed Parker, 31, merited the win but the British boxer experienced the second defeat of his 28-fight career.
Buatsi Earns Triumph in Dull Encounter
His career development has plateaued in recent years through management issues and considerable time of lack of fights.
Previously predicted as the rising talent of British boxing, he now is positioned trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under fresh management.
He began cautiously, with neither fighter willing to be aggressive in a tentative initial rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand during the bout, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the more effective rounds.
The crowd's patience decreased amid frequent holding, with Parker slipping to the canvas various instances during clinches.
The underdog ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion Carl Frampton - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor advances, but with the presence of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Contest
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding Manchester vs Manchester fight to secure the continental title.
The venue became quiet for a deeply poignant memorial prior to the bout as 10 bells tolled in honor of the city's native Hatton, who died 46 years old in recently.
It was the initial significant broadcast fight night in the urban center since Hatton's passing. As the final chime ended, the silence became a chant of "there's just one Hatton".
The competition within the ring equaled the feeling. The eventual winner was knocked down by a powerful punch directly to the jaw in the initial stage, standing uncertainly to his feet on the eight count.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in competitive blue - was injured early, significant bruising appearing under his eye as the fighters traded hard punches.
The challenger, 27, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur narrowly won the decision with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and full of heart, all the qualities their inspiration Hatton stood for.
