British light heavyweight Joshua Buatsi earned a win yet unimpressive debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive 10-round bout at the boxing arena.
But Parker found success, connecting with powerful clean blows in a contest where the styles failed to mesh, with frequent clinching marring the action.
The scoring judges had it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They prevail," Buatsi commented in the arena as he was greeted with boos from the spectators.
The Londoner got back to winning after his maiden career setback - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the Derbyshire fighter experienced the second defeat of his 28-bout professional journey.
Buatsi Claims Win in Dull Affair
Buatsi's progress has slowed in the past few years through contract problems and long spells of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to realize his potential - possibly in what seems like a final roll of the dice - under new promotional backing.
He began cautiously, with the two boxers ready to take risks in a calculated initial rounds.
Parker, whose sole prior loss came at super middleweight against John Ryder in two years ago after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the fight's midpoint, the underdog had stayed in contention, causing problems for the favorite, who operated with a protective stance to narrowly win the better stanzas.
The crowd's patience diminished during regular grabbing, with the challenger falling to the floor various instances during close exchanges.
Parker ended stronger, but multiple periods were challenging to assess. However, ex-champion the boxing analyst - commentating on Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi progresses, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol dominating the weight class, the journey to titles - based on this performance - still looks steep.
Ricky Hatton Memorial Fuels All-Manchester Battle
In the co-main event, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding Manchester vs Manchester battle to secure the continental championship.
The stadium became quiet for a deeply poignant tribute ahead of the contest as 10 bells sounded in memory of the city's native Hatton, who passed away aged 46 in last month.
It was the premier televised boxing event in the urban center since Hatton's passing. As the final chime ended, the stillness transitioned to a chant of "there's just one Hatton".
The fighting inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a left hook directly to the chin in the early round, standing uncertainly to his footing on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. From the other corner, Rea - in opposing blue - was damaged soon, noticeable damage forming under his eye as the duo traded hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with stinging uppercuts as the pace seldom decreased over the full distance.
Arthur narrowly won the verdict with scoring tallies of even score, 115-113 and 115-112, but both fighters were relentless and brave, all the qualities their hero the legend stood for.
