UK light heavyweight Joshua Buatsi made a winning yet underwhelming start to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a close 10-round bout at the Co-op Live Arena.
But Parker had his moments, landing some telling single shots in a contest where the styles never quite clicked, with excessive holding disrupting the fight.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my best display but how do champions respond? They prevail," the victor commented in the ringside as he was faced negative reactions from the crowd.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a 20th pro success.
Several boxing experts felt the challenger, 31, should have been awarded the victory but the British boxer endured the second loss of his 28-bout professional journey.
The Champion Claims Triumph in Slow Encounter
The fighter's advancement has plateaued in recent times through management issues and considerable time of lack of fights.
Previously predicted as the next star of UK boxing, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a cagey early stages.
Parker, whose single earlier setback came at super middleweight against his former opponent in two years ago after damaging his hand during the bout, was participating in his second fight at the higher weight class.
By the fight's midpoint, Parker had made it competitive, causing problems for the favorite, who utilized a solid defense to narrowly win the more effective periods.
The spectators' acceptance wore thin because of constant clinching, with Parker going down several times during close exchanges.
Parker closed well, but multiple periods were challenging to assess. Although, former world champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just one round.
Buatsi advances, but with the likes of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still appears challenging.
Hatton Homage Motivates Local Rivalry Battle
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a outstanding local rivalry fight to capture the European light-heavyweight championship.
The venue fell silent for a deeply poignant homage before the fight as a bell ceremony tolled in remembrance of the city's native Hatton, who passed away aged 46 in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the stillness became a roar of "only one Hatton".
The fighting within the ring reflected the emotion. Arthur was floored by a left hook directly to the jaw in the second round, standing uncertainly to his footing on the count of eight.
But the traditional red equipment of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was marked up quickly, heavy swelling forming under his eye as the duo exchanged punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the action rarely dropped over the full distance.
Arthur narrowly won the verdict with official scores of draw, 115-113 and clearer margin, but each competitor were relentless and brave, everything their hero the legend embodied.
