UK light-heavyweight Joshua Buatsi earned a win yet underwhelming start to life under new promoters with a points victory over Parker in Manchester.
The Olympic bronze medallist's work rate appeared to earn him a split decision in a competitive ten-round bout at the boxing arena.
But the challenger had his moments, landing some telling single shots in a fight where the approaches failed to mesh, with constant grabbing disrupting the fight.
Two judges scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my best display but what defines champions? They prevail," the victor stated in the arena as he was met by boos from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the British boxer suffered the second loss of his 28-match professional journey.
The Champion Secures Win in Uneventful Match
Buatsi's progress has slowed in the past few years through contract problems and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now stands trying to fulfil that early promise - possibly in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with both competitors prepared to take risks in a tentative early stages.
Parker, whose sole prior loss came at the lower weight class against his former opponent in two years ago after breaking his hand in the contest, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who worked behind a solid defense to narrowly win the more effective periods.
The crowd's patience diminished during regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
Parker closed well, but multiple periods were difficult to score. Nevertheless, previous titleholder the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Russian champion Bivol leading the category, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Memorial Inspires Local Rivalry Fight
In the supporting bout, Arthur beat Bradley Rea by split-decision in a excellent local rivalry fight to capture the European light heavyweight belt.
The venue grew hushed for a deeply poignant memorial ahead of the contest as a bell ceremony sounded in remembrance of the city's native Ricky Hatton, who succumbed 46 years old in last month.
It was the premier televised match card in the city since Hatton's passing. As the final chime disappeared, the silence became a roar of "there's only one Ricky Hatton".
The action during the bout matched the emotion. The eventual winner was knocked down by a powerful punch directly to the chin in the second round, rising shakily to his feet on the eight count.
But the red-colored equipment of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was injured soon, noticeable damage forming under his orbital area as the duo traded powerful shots.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action rarely dropped over twelve rounds.
The victor narrowly won the result with judges scorecards of even score, close margin and wider gap, but the two athletes were determined and full of heart, everything their hero the legend embodied.
