UK light heavyweight Joshua Buatsi made a winning yet underwhelming beginning to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a majority decision in a tight 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful clean blows in a contest where the styles didn't complement each other, with excessive holding disrupting the fight.
Two judges scored it 96-94 in favor to Buatsi, with the third a even score.
"It wasn't my best performance but what defines champions? They prevail," the victor commented in the ring as he was greeted with negative reactions from the spectators.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th career victory.
Several boxing experts believed Parker, 31, merited the decision but the British boxer endured the second loss of his 28-fight professional journey.
The Champion Claims Triumph in Uneventful Encounter
The fighter's advancement has slowed in recent times through promotional disputes and considerable time of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to realize his potential - possibly in what appears to be a last chance - under recent support.
He opened tentatively, with neither fighter prepared to take risks in a calculated initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after breaking his hand during the bout, was making just his second bout at light heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for the favorite, who worked behind a solid defense to barely take the more effective stanzas.
The audience's tolerance wore thin amid constant clinching, with the challenger falling to the floor various instances during grappling.
The underdog ended stronger, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - on this evidence - still appears challenging.
Hatton Homage Motivates Local Rivalry Fight
In the co-main event, Arthur beat Rea by close verdict in a outstanding Manchester vs Manchester battle to win the European light heavyweight championship.
The stadium fell silent for a extremely emotional tribute prior to the bout as ten bells sounded in honor of local hero Hatton, who passed away aged 46 in recently.
It was the premier televised boxing event in the city since Hatton's death. As the final chime disappeared, the stillness transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes matched the feeling. Arthur was knocked down by a left hook squarely on the jaw in the early round, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was marked up soon, heavy swelling forming under his orbital area as the fighters traded powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over 12 rounds.
Arthur barely secured the decision with official scores of draw, narrow lead and 115-112, but the two athletes were determined and full of heart, all the qualities their inspiration Hatton represented.
