British light heavyweight Joshua Buatsi earned a win yet underwhelming debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a close 10-round fight at the Manchester venue.
But the challenger found success, landing some telling single shots in a match where the approaches didn't complement each other, with excessive holding disrupting the contest.
The scoring judges had it 96-94 in favor to the winner, with the third a even score.
"It wasn't my finest showing but what defines champions? They win," Buatsi stated in the ring as he was greeted with disapproval from the audience.
The Londoner bounced back after his first professional defeat - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Various analysts believed Parker, 31, merited the win but the contender suffered the second loss of his 28-match professional journey.
Buatsi Claims Victory in Dull Encounter
His career development has plateaued in recent years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He started carefully, with the two boxers prepared to be aggressive in a tentative early stages.
Parker, whose sole prior loss came at super-middleweight against his former opponent in two years ago after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for Buatsi, who utilized a tight guard to barely take the more effective rounds.
The spectators' acceptance decreased amid frequent holding, with the challenger slipping to the canvas several times during clinches.
Parker closed well, but several stanzas were hard to judge. Although, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor advances, but with the likes of power puncher Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the co-main event, Lyndon Arthur beat Rea by split-decision in a excellent local rivalry fight to capture the European light heavyweight title.
The stadium fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony rang in honor of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the premier televised match card in the location since Hatton's passing. As the last bell ended, the quiet gave way to a roar of "there's just one Hatton".
The fighting inside the ropes matched the emotion. The eventual winner was floored by a left hook squarely on the face in the second round, getting up unsteadily to his footing on the count of eight.
But the red-colored shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his face as the fighters traded hard punches.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur narrowly won the result with scoring tallies of even score, 115-113 and 115-112, but each competitor were determined and courageous, exactly what their inspiration Hatton stood for.
