UK light-heavyweight Joshua Buatsi earned a win yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate likely gained him a split decision in a close ten-round contest at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a fight where the approaches didn't complement each other, with excessive holding spoiling the action.
The officials judged it 96-94 for to Buatsi, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They succeed," the victor stated in the arena as he was faced negative reactions from the crowd.
The British fighter got back to winning after his initial pro loss - an thrilling contest with Callum Smith in February - to claim a 20th career victory.
Several boxing experts felt the challenger, thirty-one, merited the victory but the British boxer suffered the second defeat of his 28-match career.
Buatsi Earns Win in Uneventful Affair
The fighter's advancement has stalled in recent years through promotional disputes and considerable time of lack of fights.
Previously predicted as the next star of the British fight scene, he now finds himself trying to achieve expectations - perhaps in what feels like a last chance - under fresh management.
He began cautiously, with the two boxers willing to overcommit in a calculated opening few rounds.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was making just his second fight at the higher weight class.
By the fight's midpoint, the underdog had made it competitive, causing problems for the favorite, who worked behind a tight guard to barely take the better rounds.
The spectators' acceptance diminished amid frequent holding, with Parker slipping to the canvas various instances during close exchanges.
Parker closed well, but many rounds were hard to judge. Although, former world champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
Buatsi advances, but with the presence of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still seems difficult.
Ricky Hatton Tribute Inspires Local Rivalry Fight
In the secondary fight, Arthur beat Bradley Rea by close verdict in a terrific local rivalry contest to secure the European light heavyweight title.
The arena became quiet for a profoundly moving tribute before the fight as 10 bells rang in memory of local hero Ricky Hatton, who succumbed 46 years old in recently.
It was the first major televised fight night in the location since the passing of Hatton. As the concluding sound ended, the quiet became a shout of "there's only one Ricky Hatton".
The competition inside the ropes equaled the emotion. The eventual winner was floored by a powerful punch squarely on the jaw in the initial stage, getting up unsteadily to his position on the count of eight.
But the Manchester United-red equipment of Arthur soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was marked up soon, significant bruising forming under his orbital area as the duo landed powerful shots.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace rarely dropped over twelve rounds.
The victor edged the verdict with scoring tallies of even score, narrow lead and 115-112, but both fighters were determined and brave, all the qualities their inspiration the legend stood for.
