UK light heavyweight Joshua Buatsi made a winning yet unimpressive debut to his career under recent management with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output appeared to earn him a majority decision in a competitive ten-round fight at the Manchester venue.
But the challenger had his moments, delivering effective single shots in a contest where the techniques failed to mesh, with frequent clinching marring the action.
Two judges judged it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my best display but what do champions do? They prevail," the victor commented in the ring as he was met by negative reactions from the crowd.
The Londoner got back to winning after his initial pro loss - an thrilling contest with his previous opponent in February - to claim a twentieth professional win.
Various analysts felt Parker, 31, merited the decision but the British boxer experienced the second setback of his 28-fight professional journey.
Buatsi Secures Win in Slow Encounter
Buatsi's progress has plateaued in recent times through contract problems and long spells of lack of fights.
Earlier forecast as the next star of UK boxing, he now stands trying to achieve expectations - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a cagey early stages.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after breaking his hand during the bout, was competing in only his second appearance at light-heavyweight.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who utilized a protective stance to barely take the better periods.
The audience's tolerance wore thin because of constant clinching, with the challenger going down various instances during close exchanges.
The underdog ended stronger, but many rounds were challenging to assess. Nevertheless, former world champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, awarding Buatsi just one round.
Buatsi advances, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Homage Motivates All-Manchester Fight
In the co-main event, Arthur defeated Bradley Rea by divided decision in a terrific local rivalry battle to win the continental belt.
The stadium grew hushed for a deeply poignant tribute ahead of the contest as a bell ceremony tolled in memory of local hero Ricky Hatton, who passed away aged 46 in recently.
It was the first major televised fight night in the urban center since Hatton's death. As the final chime disappeared, the silence gave way to a roar of "there's just one Hatton".
The action during the bout matched the sentiment. Arthur was sent to the canvas by a powerful punch squarely on the face in the second round, getting up unsteadily to his position on the eight count.
But the red-colored attire of the fighter soon pressed ahead again. Across the ring, the opponent - in competitive blue - was damaged quickly, significant bruising appearing under his eye as the duo traded powerful shots.
Rea, 27, connected with strong blows but the champion, 34, fought fire with fire with powerful upward punches as the intensity rarely dropped over the full distance.
Arthur barely secured the decision with judges scorecards of 114-114, close margin and wider gap, but each competitor were determined and brave, exactly what their inspiration Hatton represented.
