UK light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's punch output seemingly secured him a majority decision in a competitive 10-round fight at the Manchester venue.
But Parker found success, connecting with powerful single shots in a contest where the styles didn't complement each other, with constant grabbing marring the fight.
The officials scored it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my finest performance but what defines champions? They prevail," Buatsi commented in the ring as he was greeted with disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers felt the challenger, thirty-one, should have been awarded the decision but the contender experienced the second loss of his 28-fight career.
The Champion Claims Triumph in Uneventful Affair
The fighter's advancement has stalled in the past few years through management issues and long spells of lack of fights.
Previously predicted as the rising talent of the British fight scene, he now stands trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand during the bout, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who utilized a tight guard to narrowly win the cleaner rounds.
The audience's tolerance wore thin during frequent holding, with the challenger slipping to the canvas multiple occasions during close exchanges.
The underdog finished the stronger, but multiple periods were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for Parker, giving Buatsi just one round.
The victor progresses, but with the likes of power puncher David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Hatton Memorial Motivates Local Rivalry Battle
In the co-main event, Arthur defeated Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to win the continental title.
The arena became quiet for a extremely emotional tribute prior to the bout as a bell ceremony sounded in honor of Manchester's own Hatton, who passed away at age 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the final chime ended, the silence became a chant of "there's only one Ricky Hatton".
The action during the bout matched the emotion. The eventual winner was floored by a significant blow directly to the chin in the second round, standing uncertainly to his position on the referee's count.
But the red-colored attire of Arthur soon advanced again. From the other corner, Rea - in competitive blue - was injured soon, noticeable damage appearing under his face as the pair landed punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over the full distance.
The victor narrowly won the decision with judges scorecards of draw, close margin and clearer margin, but each competitor were persistent and brave, everything their inspiration Hatton embodied.
