British light heavyweight Joshua Buatsi made a winning yet disappointing beginning to his career under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a tight 10-round bout at the Manchester venue.
But Parker found success, landing some telling single shots in a fight where the approaches didn't complement each other, with constant grabbing marring the contest.
The scoring judges judged it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor said in the ring as he was met by negative reactions from the spectators.
The British fighter got back to winning after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers believed Parker, thirty-one, should have been awarded the decision but the British boxer suffered the second defeat of his 28-match career.
The Champion Claims Triumph in Dull Match
Buatsi's progress has stalled in the past few years through promotional disputes and considerable time of inactivity.
Previously predicted as the future of British boxing, he now is positioned trying to realize his potential - maybe in what seems like a last chance - under fresh management.
He started carefully, with the two boxers prepared to take risks in a tentative early stages.
Parker, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was competing in only his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who utilized a protective stance to narrowly win the better periods.
The crowd's patience diminished amid constant clinching, with Parker slipping to the canvas several times during grappling.
Parker closed well, but several stanzas were challenging to assess. However, ex-champion Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi progresses, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still seems difficult.
Ricky Hatton Tribute Motivates Local Rivalry Fight
In the secondary fight, Arthur beat Bradley Rea by close verdict in a outstanding Manchester vs Manchester fight to win the European light heavyweight belt.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as a bell ceremony rang in remembrance of local hero Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast boxing event in the location since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a shout of "there's just one Hatton".
The fighting inside the ropes reflected the emotion. Arthur was knocked down by a left hook squarely on the jaw in the early round, getting up unsteadily to his footing on the eight count.
But the traditional red attire of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was injured soon, heavy swelling appearing under his face as the duo traded hard punches.
Rea, 27, landed power punches but the champion, thirty-four, matched the intensity with powerful upward punches as the intensity hardly diminished over twelve rounds.
The victor edged the verdict with official scores of draw, close margin and wider gap, but the two athletes were determined and brave, all the qualities their inspiration the legend embodied.
