British light heavyweight Joshua Buatsi made a winning yet unimpressive beginning to life under fresh promotional backing with a points victory over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a majority decision in a close ten-round bout at the Manchester venue.
But Parker found success, landing some telling individual punches in a contest where the techniques failed to mesh, with excessive holding disrupting the action.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor commented in the ring as he was met by negative reactions from the crowd.
The British fighter bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a twentieth professional win.
Several boxing experts thought Parker, thirty-one, should have been awarded the victory but the British boxer experienced the second loss of his 28-bout career.
The Champion Secures Triumph in Slow Match
His career development has slowed in the past few years through contract problems and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now is positioned trying to realize his potential - maybe in what seems like a final roll of the dice - under new promotional backing.
He started carefully, with the two boxers ready to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super middleweight against his former opponent in two years ago after breaking his hand in the contest, was making just his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, causing problems for the favorite, who worked behind a protective stance to barely take the better periods.
The crowd's patience wore thin because of constant clinching, with the challenger falling to the floor several times during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. However, previous titleholder the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Motivates All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by divided decision in a excellent Manchester vs Manchester battle to win the continental belt.
The venue grew hushed for a deeply poignant homage prior to the bout as a bell ceremony tolled in memory of Manchester's own Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised match card in the city since Hatton's death. As the concluding sound ended, the quiet became a shout of "there's only one Ricky Hatton".
The action during the bout matched the sentiment. The eventual winner was knocked down by a powerful punch flush on the jaw in the initial stage, rising shakily to his footing on the count of eight.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up early, heavy swelling developing under his orbital area as the fighters landed hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the pace seldom decreased over twelve rounds.
The victor edged the decision with official scores of draw, 115-113 and 115-112, but each competitor were persistent and courageous, all the qualities their hero Hatton represented.
