UK light-heavyweight Joshua Buatsi earned a win yet unimpressive beginning to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a majority decision in a competitive 10-round contest at the Co-op Live Arena.
But Parker landed significant shots, delivering effective clean blows in a contest where the styles never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi said in the ringside as he was greeted with negative reactions from the crowd.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to secure a 20th pro success.
Some ringside observers believed Parker, 31, should have been awarded the decision but the contender experienced the second defeat of his 28-bout career.
Buatsi Claims Victory in Dull Encounter
Buatsi's progress has slowed in the past few years through contract problems and considerable time of inactivity.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to fulfil that early promise - perhaps in what feels like a last chance - under new promotional backing.
He started carefully, with neither fighter prepared to take risks in a tentative early stages.
The challenger, whose single earlier setback came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had made it competitive, causing problems for Buatsi, who worked behind a protective stance to narrowly win the more effective periods.
The spectators' acceptance wore thin amid frequent holding, with the challenger falling to the floor multiple occasions during close exchanges.
The underdog ended stronger, but many rounds were hard to judge. Although, former world champion Carl Frampton - commentating on Dazn - had it significantly in favor for the challenger, awarding Buatsi just a single round.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Hatton Memorial Inspires All-Manchester Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific local rivalry fight to capture the European light-heavyweight belt.
The stadium became quiet for a extremely emotional memorial prior to the bout as a bell ceremony tolled in honor of local hero Hatton, who passed away at age 46 in recently.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the final chime faded, the quiet became a roar of "there's only one Hatton".
The competition during the bout matched the emotion. The eventual winner was sent to the canvas by a left hook directly to the face in the early round, getting up unsteadily to his footing on the count of eight.
But the Manchester United-red equipment of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was injured early, noticeable damage forming under his orbital area as the fighters traded punishing blows.
Rea, 27, landed power punches but Arthur, thirty-four, matched the intensity with effective uppercuts as the intensity rarely dropped over 12 rounds.
The victor edged the decision with scoring tallies of 114-114, 115-113 and clearer margin, but the two athletes were relentless and courageous, everything their inspiration the legend represented.
