British light-heavyweight Joshua Buatsi secured a victory yet disappointing beginning to his career under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a close 10-round bout at the Manchester venue.
But the challenger landed significant shots, connecting with powerful single shots in a fight where the styles never quite clicked, with constant grabbing disrupting the fight.
The scoring judges had it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my greatest showing but what defines champions? They win," the victor commented in the ring as he was faced disapproval from the spectators.
The Londoner bounced back after his initial pro loss - an epic battle with his previous opponent in February - to secure a 20th career victory.
Several boxing experts believed the challenger, 31, deserved the decision but the contender suffered the second setback of his 28-fight career.
The Champion Earns Win in Dull Affair
Buatsi's progress has slowed in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to achieve expectations - maybe in what feels like a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to overcommit in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against John Ryder in two years ago after damaging his hand mid-fight, was making just his second appearance at the higher weight class.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who operated with a tight guard to narrowly win the more effective rounds.
The crowd's patience wore thin amid frequent holding, with the challenger falling to the floor various instances during grappling.
The underdog finished the stronger, but many rounds were difficult to score. However, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, scoring for Buatsi just one round.
Buatsi progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Motivates Manchester Derby Battle
In the supporting bout, Arthur defeated Rea by divided decision in a excellent Manchester vs Manchester fight to secure the continental championship.
The arena fell silent for a profoundly moving tribute prior to the bout as ten bells rang in remembrance of Manchester's own Hatton, who passed away 46 years old in recently.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the final chime faded, the stillness became a chant of "only one Hatton".
The action inside the ropes matched the sentiment. The eventual winner was sent to the canvas by a significant blow directly to the face in the second round, getting up unsteadily to his feet on the eight count.
But the traditional red shorts of the fighter soon came forward again. On the opposite side, the opponent - in rival City blue - was damaged soon, significant bruising forming under his eye as the duo exchanged powerful shots.
The challenger, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace rarely dropped over twelve rounds.
The victor edged the verdict with official scores of draw, close margin and wider gap, but each competitor were persistent and brave, all the qualities their idol the legend stood for.
