British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a tight ten-round contest at the boxing arena.
But the challenger landed significant shots, landing some telling clean blows in a fight where the techniques failed to mesh, with constant grabbing spoiling the contest.
Two judges judged it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest performance but how do champions respond? They prevail," the victor stated in the ring as he was met by negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers believed Parker, 31, merited the win but the contender suffered the second loss of his 28-bout career.
Buatsi Earns Victory in Slow Encounter
Buatsi's progress has stalled in the past few years through promotional disputes and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - maybe in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second fight at light-heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for Buatsi, who worked behind a tight guard to narrowly win the better periods.
The audience's tolerance decreased during constant clinching, with Parker going down multiple occasions during grappling.
Parker ended stronger, but several stanzas were challenging to assess. However, previous titleholder the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just one round.
The victor moves on, but with the likes of heavy hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Battle
In the supporting bout, Arthur beat Rea by divided decision in a excellent all-Manchester fight to capture the European light heavyweight championship.
The stadium grew hushed for a profoundly moving homage prior to the bout as a bell ceremony sounded in memory of local hero Hatton, who died at age 46 in last month.
It was the first major televised boxing event in the location since the passing of Hatton. As the concluding sound ended, the silence became a shout of "there's just one Ricky Hatton".
The fighting during the bout matched the feeling. The eventual winner was floored by a significant blow squarely on the face in the initial stage, getting up unsteadily to his footing on the count of eight.
But the traditional red equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was injured early, significant bruising developing under his orbital area as the pair traded hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with effective uppercuts as the action seldom decreased over twelve rounds.
The victor edged the result with judges scorecards of 114-114, 115-113 and clearer margin, but both fighters were determined and full of heart, everything their idol Hatton embodied.
