British light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a majority decision in a close ten-round bout at the boxing arena.
But the challenger landed significant shots, connecting with powerful individual punches in a match where the styles failed to mesh, with constant grabbing disrupting the contest.
The officials judged it 96-94 in favor to Buatsi, with the remaining official a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," the victor stated in the ring as he was greeted with negative reactions from the audience.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th pro success.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the Derbyshire fighter endured the second loss of his 28-bout career.
Buatsi Earns Triumph in Uneventful Encounter
His career development has plateaued in the past few years through contract problems 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 last chance - under new promotional backing.
He opened tentatively, with both competitors ready to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had stayed in contention, creating difficulties for Buatsi, who worked behind a protective stance to barely take the better periods.
The crowd's patience decreased because of constant clinching, with Parker falling to the floor several times during grappling.
Parker ended stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just a single round.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Memorial Motivates Local Rivalry Contest
In the secondary fight, Arthur beat Bradley Rea by close verdict in a excellent all-Manchester contest to win the European light heavyweight belt.
The venue became quiet for a profoundly moving homage ahead of the contest as ten bells tolled in honor of Manchester's own Hatton, who died 46 years old in September.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the concluding sound faded, the stillness became a roar of "there's just one Ricky Hatton".
The competition inside the ropes reflected the feeling. The eventual winner was floored by a left hook flush on the jaw in the second round, standing uncertainly to his feet on the referee's count.
But the Manchester United-red equipment of the fighter soon came forward again. From the other corner, Rea - in rival City blue - was marked up early, significant bruising forming under his face as the fighters exchanged punishing blows.
The challenger, 27, delivered effective strikes but the champion, 34, responded in kind with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor barely secured the decision with judges scorecards of draw, narrow lead and clearer margin, but both fighters were relentless and courageous, all the qualities their idol the legend embodied.
