UK light heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a split decision in a competitive 10-round contest at the Manchester venue.
But Parker landed significant shots, delivering effective single shots in a fight where the techniques never quite clicked, with constant grabbing spoiling the fight.
The officials scored it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my finest performance but what do champions do? They succeed," Buatsi commented in the ringside as he was met by disapproval from the audience.
The Londoner 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, should have been awarded the victory but the Derbyshire fighter suffered the second loss of his 28-bout professional journey.
Buatsi Claims Victory in Uneventful Affair
Buatsi's progress has plateaued in recent years through promotional disputes and long spells of inactivity.
Previously predicted as the future of UK boxing, he now finds himself trying to realize his potential - possibly in what appears to be a last chance - under fresh management.
He opened tentatively, with neither fighter ready to be aggressive in a cagey opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, creating difficulties for Buatsi, who operated with a protective stance to edge the better rounds.
The crowd's patience diminished amid regular grabbing, with Parker slipping to the canvas multiple occasions during clinches.
Parker closed well, but several stanzas were challenging to assess. Nevertheless, ex-champion Carl Frampton - working with Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the road to world glory - judging by this showing - still appears challenging.
Hatton Memorial Fuels Local Rivalry Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry battle to win the European light-heavyweight championship.
The arena became quiet for a deeply poignant memorial ahead of the contest as 10 bells rang in honor of the city's native Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound ended, the quiet transitioned to a roar of "there's only one Ricky Hatton".
The action during the bout reflected the feeling. Arthur was knocked down by a significant blow flush on the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the red-colored shorts of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was injured quickly, noticeable damage appearing under his face as the fighters landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, responded in kind with effective uppercuts as the action hardly diminished over twelve rounds.
The victor edged the verdict with official scores of 114-114, close margin and clearer margin, but the two athletes were relentless and brave, all the qualities their inspiration Hatton stood for.
