UK light heavyweight Joshua Buatsi earned a win yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's punch output seemingly secured him a split decision in a close 10-round contest at the boxing arena.
But the challenger had his moments, delivering effective clean blows in a fight where the approaches failed to mesh, with frequent clinching disrupting the contest.
The officials scored it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They succeed," the victor commented in the ringside as he was faced disapproval from the audience.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in February - to earn a twentieth professional win.
Several boxing experts thought the challenger, 31, merited the victory but the contender suffered the second defeat of his 28-match career.
Buatsi Secures Win in Dull Affair
His career development 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 final roll of the dice - under new promotional backing.
He opened tentatively, with the two boxers willing to be aggressive in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for Buatsi, who utilized a tight guard to barely take the cleaner rounds.
The spectators' acceptance decreased amid frequent holding, with Parker slipping to the canvas various instances during close exchanges.
Parker finished the stronger, but many rounds were challenging to assess. However, former world champion the boxing analyst - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just one round.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still appears challenging.
Hatton Memorial Inspires Local Rivalry Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by divided decision in a outstanding Manchester vs Manchester battle to secure the European light heavyweight title.
The venue fell silent for a profoundly moving tribute before the fight as 10 bells sounded in memory of local hero Ricky Hatton, who passed away aged 46 in September.
It was the premier televised match card in the location since Hatton's death. As the last bell faded, the quiet gave way to a chant of "only one Ricky Hatton".
The competition during the bout matched the sentiment. Arthur was floored by a powerful punch squarely on the jaw in the second round, rising shakily to his feet on the referee's count.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was marked up early, heavy swelling forming under his eye as the pair landed hard punches.
The challenger, twenty-seven, delivered effective strikes but Arthur, 34, fought fire with fire with stinging uppercuts as the intensity rarely dropped over twelve rounds.
Arthur edged the verdict with judges scorecards of 114-114, 115-113 and clearer margin, but both fighters were persistent and full of heart, everything their inspiration the legend represented.
