British light-heavyweight Joshua Buatsi made a winning yet underwhelming start to his career under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive ten-round bout at the boxing arena.
But the challenger landed significant shots, connecting with powerful clean blows in a contest where the styles never quite clicked, with excessive holding spoiling the fight.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my best performance but what defines champions? They win," the victor stated in the ring as he was met by negative reactions from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers felt Parker, thirty-one, should have been awarded the victory but the contender suffered the second defeat of his 28-fight professional journey.
The fighter's advancement has plateaued in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the next star of the British fight scene, he now is positioned trying to realize his potential - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers ready to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in two years ago after suffering a hand injury in the contest, was making just his second bout at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for Buatsi, who utilized a solid defense to narrowly win the more effective rounds.
The audience's tolerance diminished because of frequent holding, with Parker falling to the floor several times during clinches.
Parker closed well, but multiple periods were hard to judge. Although, former world champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
Buatsi moves on, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific Manchester vs Manchester battle to win the European light-heavyweight belt.
The arena fell silent for a deeply poignant memorial prior to the bout as 10 bells sounded in honor of local hero Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast fight night in the location since Hatton's death. As the final chime faded, the silence became a roar of "only one Ricky Hatton".
The fighting inside the ropes reflected the sentiment. The eventual winner was knocked down by a significant blow flush on the face in the second round, getting up unsteadily to his position on the count of eight.
But the traditional red equipment of Arthur soon came forward again. From the other corner, the opponent - in opposing blue - was injured early, heavy swelling appearing under his eye as the fighters landed powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace hardly diminished over the full distance.
The victor edged the result with scoring tallies of draw, narrow lead and wider gap, but the two athletes were determined and brave, all the qualities their idol Hatton embodied.
Elara Vance is a tech journalist with over a decade of experience covering AI, cybersecurity, and emerging technologies across Europe.