British light heavyweight Joshua Buatsi secured a victory yet unimpressive beginning to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive 10-round bout at the boxing arena.
But the challenger found success, delivering effective clean blows in a match where the styles didn't complement each other, with constant grabbing spoiling the action.
The scoring judges scored it 96-94 in favor to the winner, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They prevail," the victor stated in the arena as he was faced negative reactions from the spectators.
The British fighter got back to winning after his first professional defeat - an epic battle with his previous opponent in last winter - to secure a 20th career victory.
Several boxing experts felt Parker, 31, merited the win but the British boxer endured the second setback of his 28-match professional journey.
The Champion Claims Triumph in Dull Encounter
Buatsi's progress has stalled in recent years through contract problems and considerable time of lack of fights.
Earlier forecast as the rising talent of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under recent support.
He began cautiously, with both competitors ready to overcommit in a calculated initial rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for the favorite, who worked behind a tight guard to barely take the more effective periods.
The audience's tolerance decreased because of frequent holding, with Parker slipping to the canvas various instances during grappling.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Hatton Homage Motivates All-Manchester Contest
In the supporting bout, Arthur beat Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to win the continental title.
The stadium grew hushed for a extremely emotional memorial before the fight as a bell ceremony sounded in memory of local hero Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the concluding sound ended, the silence became a roar of "there's just one Hatton".
The action inside the ropes reflected the feeling. Arthur was floored by a left hook flush on the chin in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red equipment of Arthur soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, significant bruising appearing under his face as the fighters traded powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, matched the intensity with stinging uppercuts as the action seldom decreased over 12 rounds.
The victor barely secured the decision with judges scorecards of draw, close margin and 115-112, but both fighters were relentless and brave, everything their inspiration Hatton stood for.
