British light heavyweight Joshua Buatsi made a winning yet disappointing beginning to life under fresh promotional backing with a decision win over Parker in Manchester.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a close ten-round fight at the boxing arena.
But Parker had his moments, delivering effective single shots in a match where the techniques didn't complement each other, with frequent clinching marring the fight.
The scoring judges judged it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They succeed," Buatsi stated in the arena as he was faced disapproval from the crowd.
The British fighter bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a 20th pro success.
Several boxing experts felt the challenger, 31, merited the win but the Derbyshire fighter endured the second defeat of his 28-match professional journey.
Buatsi Earns Win in Uneventful Encounter
Buatsi's progress has slowed in recent times through contract problems and long spells of lack of fights.
Once tipped as the next star of British boxing, he now finds himself trying to realize his potential - possibly in what feels like a final roll of the dice - under fresh management.
He began cautiously, with the two boxers willing to take risks in a calculated initial rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was making just his second bout at the higher weight class.
By the halfway stage, Parker had kept it close, making life awkward for the favorite, who utilized a solid defense to edge the better periods.
The audience's tolerance diminished amid frequent holding, with Parker slipping to the canvas multiple occasions during clinches.
Parker finished the stronger, but many rounds were challenging to assess. Although, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter Benavidez, and Russian star Bivol ruling the division, the road to world glory - on this evidence - still appears challenging.
Hatton Homage Motivates Local Rivalry Battle
In the supporting bout, Arthur beat Bradley Rea by split-decision in a outstanding local rivalry battle to win the European light-heavyweight belt.
The stadium fell silent for a extremely emotional memorial ahead of the contest as ten bells tolled in remembrance of local hero Ricky Hatton, who passed away aged 46 in September.
It was the first major televised boxing event in the location since Hatton's passing. As the last bell disappeared, the silence transitioned to a chant of "there's only one Ricky Hatton".
The action inside the ropes equaled the emotion. The eventual winner was sent to the canvas by a left hook squarely on the jaw in the second round, rising shakily to his footing on the referee's count.
But the traditional red attire of Arthur soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up quickly, noticeable damage developing under his face as the duo landed punishing blows.
The challenger, 27, connected with strong blows but the champion, 34, responded in kind with powerful upward punches as the action seldom decreased over twelve rounds.
The victor edged the result with judges scorecards of 114-114, narrow lead and clearer margin, but each competitor were persistent and brave, exactly what their inspiration the legend stood for.
