British light heavyweight Joshua Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker had his moments, delivering effective clean blows in a contest where the styles failed to mesh, with frequent clinching disrupting the contest.
The officials judged it 96-94 for to Buatsi, with the third a even score.
"It wasn't my finest performance but what do champions do? They prevail," the victor said in the ringside as he was faced disapproval from the spectators.
The British fighter returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts believed Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second defeat of his 28-fight career.
Buatsi Secures Triumph in Uneventful Encounter
Buatsi's progress has plateaued in recent years through contract problems and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with the two boxers prepared to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against his former opponent in two years ago after suffering a hand injury during the bout, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a solid defense to edge the better rounds.
The audience's tolerance decreased during regular grabbing, with the challenger going down various instances during grappling.
The underdog closed well, but many rounds were challenging to assess. Although, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian star Dmitry Bivol ruling the division, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Memorial Motivates Manchester Derby Battle
In the supporting bout, Arthur overcame Rea by close verdict in a terrific Manchester vs Manchester battle to capture the continental belt.
The arena fell silent for a profoundly moving memorial before the fight as a bell ceremony rang in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in last month.
It was the premier televised boxing event in the location since the passing of Hatton. As the last bell disappeared, the stillness gave way to a chant of "only one Ricky Hatton".
The fighting within the ring equaled the emotion. The eventual winner was sent to the canvas by a powerful punch flush on the chin in the second round, getting up unsteadily to his position on the referee's count.
But the red-colored shorts of Arthur soon advanced again. Across the ring, Rea - in rival City blue - was injured early, noticeable damage appearing under his face as the fighters traded powerful shots.
Rea, 27, delivered effective strikes but the champion, 34, fought fire with fire with stinging uppercuts as the pace seldom decreased over twelve rounds.
Arthur narrowly won the decision with official scores of even score, 115-113 and clearer margin, but both fighters were relentless and courageous, all the qualities their hero Hatton embodied.
