British light-heavyweight Joshua Buatsi secured a victory yet underwhelming start to life under new promoters with a decision win over Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a judges' verdict in a tight ten-round bout at the Manchester venue.
But Parker had his moments, landing some telling single shots in a contest where the styles never quite clicked, with frequent clinching spoiling the fight.
The scoring judges scored it 96-94 for to Buatsi, with the third a even score.
"It wasn't my greatest performance but what defines champions? They succeed," Buatsi said in the ringside as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his initial pro loss - an thrilling contest with his previous opponent in last winter - to claim a 20th pro success.
Various analysts believed the challenger, thirty-one, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-match career.
Buatsi Earns Triumph in Dull Affair
The fighter's advancement has slowed in recent times through contract problems and considerable time of inactivity.
Earlier forecast as the next star of British boxing, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under fresh management.
He opened tentatively, with both competitors prepared to overcommit in a tentative initial rounds.
Parker, whose sole prior loss came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to narrowly win the better rounds.
The crowd's patience diminished during regular grabbing, with the challenger going down multiple occasions during clinches.
The underdog closed well, but multiple periods were difficult to score. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Tribute Motivates Manchester Derby Contest
In the secondary fight, Arthur defeated Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to win the European light heavyweight championship.
The venue grew hushed for a profoundly moving tribute prior to the bout as 10 bells sounded in remembrance of the city's native Ricky Hatton, who succumbed at age 46 in recently.
It was the first major televised boxing event in the city since Hatton's death. As the concluding sound faded, the quiet gave way to a chant of "there's just one Hatton".
The action during the bout reflected the feeling. The eventual winner was knocked down by a left hook flush on the chin in the second round, getting up unsteadily to his footing on the eight count.
But the traditional red attire of the fighter soon came forward again. Across the ring, Rea - in rival City blue - was marked up early, significant bruising forming under his face as the pair exchanged powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity rarely dropped over 12 rounds.
Arthur barely secured the verdict with judges scorecards of draw, narrow lead and 115-112, but the two athletes were relentless and full of heart, everything their inspiration Hatton stood for.
