British light heavyweight Joshua Buatsi secured a victory yet unimpressive debut to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round fight at the boxing arena.
But the challenger found success, delivering effective clean blows in a fight where the techniques never quite clicked, with excessive holding marring the action.
The scoring judges judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best showing but what do champions do? They prevail," the victor said in the ring as he was met by disapproval from the crowd.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Some ringside observers believed the challenger, thirty-one, should have been awarded the decision but the British boxer experienced the second defeat of his 28-bout professional journey.
Buatsi Earns Victory in Slow Affair
His career development has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now is positioned trying to achieve expectations - possibly in what appears to be a last chance - under new promotional backing.
He opened tentatively, with neither fighter prepared to overcommit in a calculated early stages.
Parker, whose only previous defeat came at the lower weight class against his former opponent in 2022 after breaking his hand in the contest, was making just his second fight at light heavyweight.
By the halfway stage, Parker had made it competitive, causing problems for the favorite, who operated with a solid defense to edge the cleaner stanzas.
The audience's tolerance decreased amid regular grabbing, with Parker going down several times during grappling.
The underdog closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - working with Dazn - had it particularly wide for Parker, giving Buatsi just a single round.
The victor progresses, but with the presence of power puncher Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Hatton Memorial Inspires Local Rivalry Fight
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry battle to capture the European light-heavyweight belt.
The venue grew hushed for a deeply poignant homage prior to the bout as a bell ceremony tolled in honor of Manchester's own Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the city since Hatton's death. As the concluding sound disappeared, the quiet gave way to a chant of "there's only one Ricky Hatton".
The fighting inside the ropes equaled the feeling. Arthur was sent to the canvas by a significant blow directly to the jaw in the second round, getting up unsteadily to his footing on the eight count.
But the red-colored attire of Arthur soon came forward again. From the other corner, Rea - in opposing blue - was damaged quickly, heavy swelling developing under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the action hardly diminished over twelve rounds.
Arthur narrowly won the result with scoring tallies of even score, 115-113 and wider gap, but both fighters were determined and brave, everything their inspiration Hatton represented.
