UK light heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under new promoters with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a close 10-round contest at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling individual punches in a contest where the styles didn't complement each other, with excessive holding marring the contest.
The officials scored it 96-94 to the winner, with the remaining official a 95-95.
"It wasn't my best performance but what do champions do? They succeed," 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 epic battle with his previous opponent in last winter - to earn a 20th career victory.
Some ringside observers believed Parker, thirty-one, deserved the decision but the contender suffered the second defeat of his 28-fight professional journey.
His career development has slowed in recent years through management issues and considerable time of inactivity.
Once tipped as the future of the British fight scene, he now is positioned trying to realize his potential - maybe in what feels like a ultimate opportunity - under recent support.
He began cautiously, with the two boxers willing to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a protective stance to edge the better stanzas.
The audience's tolerance wore thin because of regular grabbing, with Parker going down multiple occasions during close exchanges.
Parker closed well, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a excellent local rivalry fight to win the European light-heavyweight belt.
The arena became quiet for a profoundly moving homage before the fight as 10 bells tolled in honor of the city's native Ricky Hatton, who passed away 46 years old in last month.
It was the premier televised boxing event in the urban center since Hatton's death. As the concluding sound disappeared, the silence gave way to a roar of "only one Ricky Hatton".
The competition during the bout equaled the sentiment. Arthur was floored by a significant blow squarely on the face in the initial stage, rising shakily to his feet on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was damaged early, noticeable damage appearing under his orbital area as the pair exchanged hard punches.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with effective uppercuts as the action seldom decreased over 12 rounds.
The victor edged the decision with judges scorecards of draw, close margin and 115-112, but both fighters were relentless and courageous, exactly what their inspiration Hatton embodied.
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