British light-heavyweight Joshua Buatsi secured a victory yet unimpressive start to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But the challenger had his moments, delivering effective single shots in a match where the styles never quite clicked, with excessive holding spoiling the action.
The officials had it 96-94 to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," Buatsi stated in the ringside as he was met by disapproval from the spectators.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Some ringside observers believed Parker, thirty-one, merited the win but the contender suffered the second loss of his 28-match professional journey.
Buatsi Earns Victory in Dull Affair
The fighter's advancement has slowed in recent times through promotional disputes and long spells of lack of fights.
Once tipped as the future of UK boxing, he now stands trying to achieve expectations - maybe in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a cagey early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after breaking his hand in the contest, was making just his second bout at light heavyweight.
By the fight's midpoint, the underdog had kept it close, making life awkward for the favorite, who utilized a tight guard to barely take the more effective periods.
The spectators' acceptance diminished during frequent holding, with the challenger slipping to the canvas various instances during close exchanges.
Parker closed well, but many rounds were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Hatton Homage Motivates Manchester Derby Battle
In the secondary fight, Arthur overcame Rea by close verdict in a excellent local rivalry battle to capture the European light heavyweight championship.
The stadium became quiet for a deeply poignant memorial prior to the bout as 10 bells sounded in remembrance of local hero Hatton, who passed away 46 years old in recently.
It was the premier televised match card in the location since Hatton's passing. As the concluding sound ended, the silence became a chant of "only one Hatton".
The competition within the ring equaled the emotion. The eventual winner was floored by a significant blow flush on the jaw in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red shorts of the fighter soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged early, heavy swelling developing under his face as the duo exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, 34, fought fire with fire with stinging uppercuts as the pace rarely dropped over the full distance.
The victor edged the decision with scoring tallies of draw, narrow lead and wider gap, but each competitor were persistent and full of heart, everything their hero Hatton stood for.
