UK light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to his career under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a close ten-round contest at the boxing arena.
But Parker had his moments, landing some telling single shots in a match where the approaches never quite clicked, with excessive holding marring the fight.
The scoring judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my finest performance but how do champions respond? They prevail," the victor said in the ringside as he was met by boos from the audience.
The Londoner got back to winning after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers felt Parker, thirty-one, deserved the decision but the Derbyshire fighter endured the second setback of his 28-bout professional journey.
Buatsi Claims Win in Uneventful Encounter
The fighter's advancement has stalled in recent years through promotional disputes and long spells of lack of fights.
Earlier forecast as the next star of British boxing, he now finds himself trying to achieve expectations - possibly in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers prepared to take risks in a calculated early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand in the contest, was making just his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to barely take the cleaner periods.
The crowd's patience decreased during regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog finished the stronger, but multiple periods were difficult to score. Although, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian star Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Inspires Local Rivalry Fight
In the co-main event, Arthur beat Bradley Rea by close verdict in a excellent Manchester vs Manchester fight to secure the continental belt.
The venue grew hushed for a deeply poignant homage prior to the bout as ten bells tolled in honor of local hero Ricky Hatton, who succumbed aged 46 in last month.
It was the premier televised boxing event in the city since the passing of Hatton. As the final chime disappeared, the quiet gave way to a roar of "there's just one Hatton".
The fighting inside the ropes matched the feeling. Arthur was sent to the canvas by a significant blow squarely on the chin in the second round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured soon, noticeable damage forming under his face as the duo exchanged powerful shots.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with effective uppercuts as the intensity hardly diminished over twelve rounds.
Arthur barely secured the verdict with official scores of even score, 115-113 and wider gap, but the two athletes were relentless and brave, everything their idol Hatton embodied.
