UK light-heavyweight Joshua Buatsi made a winning yet underwhelming start to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a competitive 10-round fight at the boxing arena.
But Parker had his moments, connecting with powerful single shots in a match where the techniques failed to mesh, with frequent clinching marring the action.
The officials had it 96-94 for to the winner, with the third a 95-95 draw.
"It wasn't my finest display but how do champions respond? They prevail," Buatsi stated in the ringside as he was met by boos from the spectators.
The Londoner got back to winning after his initial pro loss - an memorable fight with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers felt the challenger, 31, deserved the decision but the British boxer suffered the second loss of his 28-fight professional journey.
Buatsi Claims Win in Dull Match
Buatsi's progress has plateaued in the past few years through management issues and extended periods of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with both competitors ready to be aggressive in a cagey early stages.
Parker, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who worked behind a tight guard to edge the better periods.
The spectators' acceptance diminished because of regular grabbing, with the challenger slipping to the canvas various instances during grappling.
Parker ended stronger, but many rounds were challenging to assess. Nevertheless, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
Buatsi advances, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Fuels Manchester Derby Contest
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a outstanding all-Manchester battle to win the European light-heavyweight championship.
The arena became quiet for a profoundly moving homage before the fight as ten bells tolled in honor of local hero Hatton, who succumbed at age 46 in recently.
It was the first major televised boxing event in the location since Hatton's death. As the concluding sound ended, the stillness became a roar of "there's only one Hatton".
The competition within the ring reflected the emotion. Arthur was floored by a left hook squarely on the face in the second round, standing uncertainly to his position on the referee's count.
But the traditional red attire of the fighter soon advanced again. On the opposite side, the opponent - in opposing blue - was marked up quickly, heavy swelling forming under his orbital area as the pair landed powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the result with scoring tallies of draw, close margin and clearer margin, but the two athletes were determined and courageous, exactly what their inspiration the legend embodied.
