UK light-heavyweight Joshua Buatsi earned a win yet underwhelming debut to his career under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a split decision in a tight ten-round contest at the boxing arena.
But Parker had his moments, connecting with powerful individual punches in a fight where the techniques failed to mesh, with frequent clinching disrupting the fight.
The scoring judges judged it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my best performance but what do champions do? They win," the victor said in the ringside as he was greeted with disapproval from the crowd.
The Londoner bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Some ringside observers thought the challenger, 31, should have been awarded the victory but the Derbyshire fighter suffered the second defeat of his 28-match professional journey.
Buatsi Secures Triumph in Dull Encounter
The fighter's advancement has slowed in the past few years through management issues and considerable time of inactivity.
Earlier forecast as the next star of UK boxing, he now finds himself trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to be aggressive in a calculated initial rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand during the bout, was competing in only his second appearance at the higher weight class.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who utilized a protective stance to edge the more effective rounds.
The crowd's patience diminished amid frequent holding, with the challenger going down several times during close exchanges.
Parker finished the stronger, but many rounds were hard to judge. However, former world champion Carl Frampton - providing analysis for Dazn - had it particularly wide for Parker, awarding Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still seems difficult.
Ricky Hatton Homage Motivates Local Rivalry Fight
In the supporting bout, Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester battle to win the continental championship.
The venue grew hushed for a extremely emotional tribute before the fight as ten bells sounded in remembrance of Manchester's own Hatton, who died 46 years old in last month.
It was the initial significant broadcast match card in the city since Hatton's passing. As the final chime ended, the silence became a shout of "there's just one Hatton".
The action within the ring matched the feeling. Arthur was sent to the canvas by a significant blow flush on the face in the early round, getting up unsteadily to his position on the eight count.
But the traditional red attire of Arthur soon advanced again. On the opposite side, the opponent - in opposing blue - was injured quickly, heavy swelling appearing under his orbital area as the fighters traded punishing blows.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace hardly diminished over twelve rounds.
Arthur narrowly won the decision with official scores of 114-114, narrow lead and clearer margin, but both fighters were relentless and full of heart, exactly what their hero the legend stood for.
