British light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive ten-round fight at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful single shots in a match where the styles never quite clicked, with constant grabbing spoiling the action.
The scoring judges judged it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest performance but how do champions respond? They prevail," Buatsi said in the arena as he was greeted with boos from the spectators.
The Londoner bounced back after his first professional defeat - an memorable fight with his previous opponent in last winter - to secure a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the contender experienced the second setback of his 28-bout career.
Buatsi Secures Victory in Uneventful Encounter
Buatsi's progress has stalled in recent times through management issues and long spells of inactivity.
Previously predicted as the next star of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what feels like a final roll of the dice - under fresh management.
He opened tentatively, with neither fighter willing to be aggressive in a calculated opening few rounds.
Parker, whose single earlier setback came at super-middleweight against his former opponent in two years ago after breaking his hand during the bout, was competing in only his second bout at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for Buatsi, who operated with a solid defense to edge the cleaner rounds.
The spectators' acceptance diminished because of regular grabbing, with Parker going down several times during clinches.
Parker finished the stronger, but many rounds were hard to judge. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor moves on, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Lyndon Arthur beat Rea by close verdict in a excellent local rivalry battle to secure the European light heavyweight title.
The venue fell silent for a extremely emotional homage prior to the bout as a bell ceremony sounded in honor of local hero Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the concluding sound ended, the silence became a chant of "there's just one Ricky Hatton".
The competition within the ring reflected the feeling. Arthur was knocked down by a powerful punch directly to the face in the initial stage, getting up unsteadily to his feet on the referee's count.
But the red-colored shorts of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was damaged quickly, significant bruising forming under his face as the duo traded hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace rarely dropped over twelve rounds.
Arthur edged the result with judges scorecards of 114-114, close margin and wider gap, but both fighters were determined and brave, exactly what their inspiration Hatton represented.
