British light heavyweight Joshua Buatsi earned a win yet unimpressive beginning to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output likely gained him a split decision in a close 10-round contest at the boxing arena.
But the challenger had his moments, delivering effective clean blows in a fight where the approaches never quite clicked, with excessive holding spoiling the contest.
The scoring judges judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my best performance but what defines champions? They prevail," Buatsi said in the arena as he was faced boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an memorable fight with his previous opponent in February - to claim a 20th career victory.
Various analysts felt Parker, 31, merited the win but the contender endured the second loss of his 28-bout career.
Buatsi Secures Victory in Uneventful Affair
His career development has plateaued in recent times through management issues and considerable time of inactivity.
Once tipped as the future of UK boxing, he now stands trying to fulfil that early promise - maybe in what appears to be a ultimate opportunity - under fresh management.
He began cautiously, with both competitors prepared to be aggressive in a cagey initial rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was participating in his second bout at light heavyweight.
By the fight's midpoint, the underdog had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to narrowly win the more effective rounds.
The audience's tolerance diminished amid constant clinching, with the challenger going down multiple occasions during grappling.
Parker finished the stronger, but many rounds were challenging to assess. However, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, giving Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still seems difficult.
Hatton Tribute Motivates Manchester Derby Fight
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a terrific all-Manchester battle to capture the continental title.
The arena became quiet for a profoundly moving homage ahead of the contest as ten bells sounded in memory of local hero Ricky Hatton, who passed away at age 46 in last month.
It was the first major televised fight night in the location since Hatton's death. As the final chime faded, the quiet became a chant of "there's only one Hatton".
The fighting within the ring matched the sentiment. Arthur was knocked down by a significant blow flush on the chin in the early round, standing uncertainly to his feet on the referee's count.
But the traditional red attire of the fighter soon came forward again. On the opposite side, the opponent - in rival City blue - was injured early, significant bruising developing under his face as the duo landed punishing blows.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with stinging uppercuts as the pace hardly diminished over twelve rounds.
Arthur edged the decision with scoring tallies of even score, close margin and wider gap, but both fighters were persistent and brave, everything their hero the legend represented.
