British light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level appeared to earn him a majority decision in a tight ten-round fight at the boxing arena.
But the challenger found success, connecting with powerful clean blows in a fight where the approaches never quite clicked, with excessive holding marring the fight.
Two judges judged it 96-94 to Buatsi, with the third a 95-95.
"It wasn't my finest showing but what defines champions? They prevail," Buatsi commented in the ringside as he was greeted with boos from the spectators.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with Callum Smith in February - to earn a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the victory but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
The Champion Secures Victory in Slow Affair
The fighter's advancement has stalled in recent times through management issues and considerable time of lack of fights.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what appears to be a ultimate opportunity - under fresh management.
He opened tentatively, with neither fighter ready to overcommit in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the halfway stage, Parker had made it competitive, creating difficulties for the favorite, who operated with a protective stance to edge the better periods.
The crowd's patience diminished because of constant clinching, with Parker falling to the floor various instances during grappling.
Parker closed well, but several stanzas were challenging to assess. However, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, awarding Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter Benavidez, and Russian champion Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Hatton Homage Motivates Local Rivalry Contest
In the co-main event, Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester contest to secure the continental belt.
The venue grew hushed for a profoundly moving homage ahead of the contest as ten bells sounded in honor of Manchester's own Ricky Hatton, who died 46 years old in recently.
It was the first major televised boxing event in the location since Hatton's death. As the last bell ended, the quiet became a shout of "there's just one Hatton".
The action during the bout reflected the emotion. The eventual winner was floored by a left hook directly to the face in the early round, rising shakily to his footing on the count of eight.
But the red-colored attire of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was damaged early, noticeable damage forming under his orbital area as the fighters landed hard punches.
Rea, twenty-seven, landed power punches but Arthur, thirty-four, fought fire with fire with effective uppercuts as the pace rarely dropped over the full distance.
The victor barely secured the decision with official scores of draw, 115-113 and clearer margin, but each competitor were relentless and courageous, exactly what their inspiration Hatton represented.
