British light-heavyweight Joshua Buatsi made a winning yet disappointing beginning 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 split decision in a close ten-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful clean blows in a match where the techniques didn't complement each other, with frequent clinching disrupting the contest.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what do champions do? They prevail," Buatsi stated in the ringside as he was met by boos from the audience.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts thought Parker, 31, should have been awarded the win but the contender endured the second loss of his 28-bout career.
Buatsi Secures Victory in Uneventful Affair
His career development has plateaued in recent times through management issues and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now is positioned trying to realize his potential - perhaps in what seems like a last chance - under recent support.
He opened tentatively, with the two boxers ready to take risks in a cagey opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only 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 protective stance to narrowly win the more effective rounds.
The spectators' acceptance decreased because of constant clinching, with the challenger slipping to the canvas various instances during clinches.
The underdog closed well, but many rounds were challenging to assess. Although, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, awarding Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Homage Fuels Manchester Derby Fight
In the co-main event, Arthur defeated Rea by split-decision in a outstanding local rivalry contest to capture the continental belt.
The venue became quiet for a profoundly moving homage prior to the bout as ten bells sounded in remembrance of the city's native Ricky Hatton, who died 46 years old in last month.
It was the first major televised match card in the city since Hatton's death. As the final chime faded, the silence transitioned to a shout of "there's just one Ricky Hatton".
The fighting within the ring equaled the feeling. Arthur was knocked down by a significant blow flush on the face in the second round, getting up unsteadily to his position on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in opposing blue - was damaged soon, significant bruising forming under his face as the duo exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over the full distance.
The victor barely secured the verdict with scoring tallies of even score, close margin and 115-112, but both fighters were persistent and brave, everything their hero Hatton stood for.
