UK light-heavyweight Joshua Buatsi made a winning yet disappointing debut to his career under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a close ten-round fight at the Co-op Live Arena.
But the challenger found success, delivering effective clean blows in a contest where the techniques never quite clicked, with constant grabbing disrupting the action.
Two judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best performance but what do champions do? They succeed," the victor said in the arena as he was met by negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in last winter - to earn a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the British boxer experienced the second setback of his 28-bout career.
Buatsi Earns Win in Slow Encounter
The fighter's advancement has slowed in recent years through management issues and considerable time of lack of fights.
Once tipped as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what seems like a ultimate opportunity - under fresh management.
He began cautiously, with both competitors ready to overcommit in a cagey opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was competing in only his second bout at light heavyweight.
By the halfway stage, the underdog had kept it close, causing problems for the favorite, who operated with a tight guard to narrowly win the cleaner stanzas.
The audience's tolerance decreased because of regular grabbing, with Parker going down multiple occasions during grappling.
The underdog closed well, but multiple periods were hard to judge. Although, previous titleholder the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just a single round.
The victor advances, but with the caliber of hard hitter David Benavidez, and Russian champion Bivol dominating the weight class, the road to world glory - judging by this showing - still seems difficult.
Hatton Memorial Inspires Local Rivalry Fight
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a outstanding local rivalry contest to capture the European light-heavyweight belt.
The arena became quiet for a profoundly moving homage before the fight as 10 bells sounded in remembrance of local hero Hatton, who passed away 46 years old in last month.
It was the first major televised boxing event in the location since the passing of Hatton. As the concluding sound faded, the stillness gave way to a roar of "there's only one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was knocked down by a left hook flush on the chin in the initial stage, getting up unsteadily to his feet on the eight count.
But the red-colored equipment of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was marked up soon, significant bruising appearing under his eye as the duo landed powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the intensity hardly diminished over 12 rounds.
Arthur edged the decision with judges scorecards of draw, narrow lead and clearer margin, but both fighters were determined and brave, all the qualities their hero the legend stood for.
