UK light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under recent management with a decision win over Parker in the Manchester arena.
The Olympic medal winner's punch output appeared to earn him a majority decision in a close 10-round fight at the Manchester venue.
But the challenger landed significant shots, landing some telling clean blows in a contest where the techniques failed to mesh, with constant grabbing disrupting the action.
Two judges had it 96-94 in favor to the winner, with the final judge a even score.
"It wasn't my best performance but what defines champions? They succeed," the victor said in the ringside as he was greeted with disapproval from the audience.
The British fighter got back to winning after his maiden career setback - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Various analysts felt Parker, 31, merited the victory but the British boxer suffered the second setback of his 28-bout professional journey.
The Champion Claims Triumph in Uneventful Affair
His career development has stalled in recent times through contract problems and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after damaging his hand during the bout, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who operated with a solid defense to narrowly win the cleaner periods.
The audience's tolerance diminished because of constant clinching, with the challenger falling to the floor various instances during clinches.
The underdog closed well, but many rounds were difficult to score. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just a single round.
The victor advances, but with the presence of heavy hitter Benavidez, and Eastern European fighter Bivol dominating the weight class, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Battle
In the co-main event, Arthur beat Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the European light-heavyweight championship.
The stadium became quiet for a profoundly moving tribute prior to the bout as 10 bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away at age 46 in September.
It was the premier televised boxing event in the city since Hatton's passing. As the concluding sound faded, the quiet gave way to a chant of "only one Hatton".
The competition within the ring equaled the feeling. Arthur was knocked down by a powerful punch squarely on the jaw in the second round, getting up unsteadily to his footing on the referee's count.
But the traditional red shorts of Arthur soon advanced again. On the opposite side, Rea - in opposing blue - was injured quickly, heavy swelling appearing under his face as the pair traded powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with powerful upward punches as the action rarely dropped over twelve rounds.
The victor edged the decision with official scores of draw, 115-113 and 115-112, but both fighters were persistent and full of heart, everything their idol the legend stood for.
