British light-heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive ten-round bout at the Manchester venue.
But Parker found success, connecting with powerful individual punches in a fight where the styles didn't complement each other, with constant grabbing spoiling the fight.
The scoring judges had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best showing but how do champions respond? They prevail," Buatsi stated in the ring as he was faced boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with Callum Smith in last winter - to secure a 20th career victory.
Some ringside observers believed Parker, thirty-one, should have been awarded the victory but the contender endured the second loss of his 28-match career.
Buatsi Claims Win in Dull Affair
The fighter's advancement has stalled in recent years through management issues and long spells of inactivity.
Previously predicted as the future of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what feels like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers prepared to be aggressive in a calculated early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for Buatsi, who operated with a protective stance to barely take the cleaner rounds.
The crowd's patience diminished amid frequent holding, with the challenger going down multiple occasions during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, giving Buatsi just one round.
The victor advances, but with the presence of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Motivates Local Rivalry Battle
In the supporting bout, Arthur overcame Rea by split-decision in a outstanding local rivalry battle to capture the European light-heavyweight belt.
The stadium became quiet for a deeply poignant memorial prior to the bout as ten bells sounded in memory of local hero Ricky Hatton, who died aged 46 in recently.
It was the first major televised fight night in the city since the passing of Hatton. As the final chime ended, the silence transitioned to a chant of "there's only one Ricky Hatton".
The competition inside the ropes equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the jaw in the second round, rising shakily to his footing on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in rival City blue - was marked up soon, significant bruising developing under his face as the pair traded powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with effective uppercuts as the pace seldom decreased over 12 rounds.
The victor narrowly won the decision with judges scorecards of even score, narrow lead and wider gap, but both fighters were persistent and courageous, everything their inspiration Hatton represented.
