British light heavyweight Joshua Buatsi made a winning yet disappointing debut to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic medal winner's work rate seemingly secured him a split decision in a competitive 10-round contest at the Manchester venue.
But the challenger had his moments, landing some telling individual punches in a contest where the techniques didn't complement each other, with frequent clinching disrupting the fight.
The officials had it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my finest display but how do champions respond? They succeed," the victor stated in the arena as he was met by boos from the crowd.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to earn a 20th pro success.
Various analysts felt the challenger, 31, merited the victory but the Derbyshire fighter suffered the second loss of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Encounter
The fighter's advancement has plateaued in the past few years through contract problems and considerable time of inactivity.
Once tipped as the next star of the British fight scene, he now finds himself trying to achieve expectations - maybe in what feels like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter ready to overcommit in a cagey initial rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had kept it close, causing problems for Buatsi, who operated with a tight guard to barely take the better rounds.
The spectators' acceptance wore thin because of regular grabbing, with the challenger falling to the floor multiple occasions during clinches.
The underdog ended stronger, but multiple periods were challenging to assess. Although, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
The victor progresses, but with the likes of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still looks steep.
Hatton Homage Fuels All-Manchester Fight
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester contest to win the European light-heavyweight belt.
The stadium fell silent for a profoundly moving homage prior to the bout as a bell ceremony tolled in remembrance of the city's native Hatton, who died 46 years old in September.
It was the initial significant broadcast fight night in the city since Hatton's death. As the last bell faded, the quiet gave way to a shout of "there's only one Hatton".
The fighting within the ring reflected the sentiment. Arthur was sent to the canvas by a powerful punch directly to the chin in the early round, getting up unsteadily to his position on the referee's count.
But the traditional red equipment of Arthur soon advanced again. On the opposite side, Rea - in opposing blue - was marked up soon, significant bruising developing under his eye as the fighters landed hard punches.
Rea, twenty-seven, connected with strong blows but the champion, thirty-four, fought fire with fire with effective uppercuts as the action rarely dropped over 12 rounds.
Arthur barely secured the decision with scoring tallies of 114-114, close margin and clearer margin, but the two athletes were determined and brave, exactly what their inspiration Hatton represented.
