British light-heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive ten-round bout at the boxing arena.
But the challenger had his moments, delivering effective single shots in a fight where the techniques never quite clicked, with frequent clinching spoiling the fight.
The officials had it 96-94 to the winner, with the third a 95-95.
"It wasn't my best performance but what defines champions? They succeed," Buatsi said in the ring as he was faced negative reactions from the audience.
The Londoner got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts thought the challenger, 31, merited the victory but the Derbyshire fighter suffered the second loss of his 28-bout career.
Buatsi Secures Victory in Dull Match
Buatsi's progress has stalled in the past few years through contract problems and extended periods of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a cagey early stages.
Parker, whose single earlier setback came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who operated with a protective stance to edge the better stanzas.
The spectators' acceptance diminished amid regular grabbing, with Parker falling to the floor multiple occasions during grappling.
Parker closed well, but multiple periods were hard to judge. Although, former world champion the boxing analyst - working with Dazn - had it particularly wide for Parker, giving Buatsi just only one stanza.
The victor advances, but with the presence of hard hitter Benavidez, and Russian star Bivol ruling the division, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Motivates Manchester Derby Battle
In the supporting bout, Arthur beat Rea by divided decision in a outstanding all-Manchester battle to win the European light-heavyweight title.
The arena became quiet for a profoundly moving homage prior to the bout as a bell ceremony rang in remembrance of the city's native Ricky Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast boxing event 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 fighting during the bout reflected the sentiment. The eventual winner was knocked down by a powerful punch directly to the jaw in the second round, getting up unsteadily to his feet on the count of eight.
But the traditional red shorts of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was marked up quickly, significant bruising developing under his orbital area as the duo traded powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the pace rarely dropped over 12 rounds.
The victor edged the result with scoring tallies of 114-114, 115-113 and 115-112, but the two athletes were relentless and full of heart, everything their idol the legend stood for.
