British light heavyweight Joshua Buatsi made a winning yet underwhelming start to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a competitive 10-round contest at the Manchester venue.
But the challenger found success, delivering effective single shots in a fight where the styles failed to mesh, with excessive holding marring the fight.
The officials judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but what do champions do? They prevail," the victor said in the ring as he was faced negative reactions from the audience.
The Londoner bounced back after his maiden career setback - an memorable fight with his previous opponent in last winter - to earn a 20th career victory.
Various analysts felt the challenger, 31, deserved the victory but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Secures Triumph in Slow Match
Buatsi's progress has plateaued in recent years through management issues and considerable time of inactivity.
Earlier forecast as the future of the British fight scene, he now stands trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He started carefully, with both competitors ready to take risks in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second bout at light-heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to edge the more effective stanzas.
The spectators' acceptance diminished during frequent holding, with Parker going down several times during close exchanges.
The underdog closed well, but many rounds were challenging to assess. Although, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Hatton Memorial Motivates All-Manchester Contest
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a outstanding Manchester vs Manchester battle to capture the continental belt.
The stadium grew hushed for a profoundly moving homage ahead of the contest as a bell ceremony tolled in honor of the city's native Ricky Hatton, who passed away 46 years old in last month.
It was the premier televised match card in the location since Hatton's death. As the concluding sound faded, the silence gave way to a chant of "there's only one Ricky Hatton".
The competition within the ring matched the feeling. Arthur was floored by a significant blow directly to the jaw in the early round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red shorts of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was marked up soon, significant bruising forming under his face as the fighters traded powerful shots.
Rea, 27, connected with strong blows but Arthur, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur narrowly won the decision with official scores of draw, 115-113 and 115-112, but the two athletes were persistent and courageous, everything their hero Hatton represented.
