British light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning 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 tight 10-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling clean blows in a fight where the styles never quite clicked, with excessive holding marring the contest.
The scoring judges judged it 96-94 to the winner, with the final judge a 95-95.
"It wasn't my greatest performance but what defines champions? They win," Buatsi stated in the ring as he was met by boos from the spectators.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts felt the challenger, thirty-one, should have been awarded the decision but the British boxer suffered the second loss of his 28-bout career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has slowed in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the next star of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter ready to be aggressive in a tentative opening few rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was making just his second bout at light heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who utilized a protective stance to edge the better stanzas.
The audience's tolerance diminished because of regular grabbing, with Parker going down various instances during close exchanges.
The underdog closed well, but several stanzas were difficult to score. However, ex-champion Carl Frampton - working with Dazn - had it significantly in favor for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Manchester Derby Fight
In the secondary fight, Arthur defeated Rea by split-decision in a outstanding local rivalry battle to win the continental championship.
The venue fell silent for a profoundly moving homage before the fight as ten bells rang in remembrance of Manchester's own Hatton, who passed away at age 46 in September.
It was the initial significant broadcast fight night in the location since Hatton's passing. As the concluding sound disappeared, the quiet gave way to a roar of "only one Hatton".
The competition during the bout reflected the sentiment. Arthur was floored by a significant blow flush on the chin in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was injured quickly, heavy swelling appearing under his face as the duo landed hard punches.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the pace seldom decreased over the full distance.
Arthur barely secured the verdict with judges scorecards of even score, narrow lead and 115-112, but the two athletes were persistent and full of heart, exactly what their hero the legend embodied.
