UK light heavyweight Joshua Buatsi earned a win yet disappointing beginning to life under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a tight 10-round fight at the Manchester venue.
But Parker landed significant shots, delivering effective individual punches in a match where the approaches didn't complement each other, with constant grabbing marring the action.
Two judges judged it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best display but what do champions do? They prevail," the victor stated in the ringside as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with his previous opponent in February - to secure a twentieth professional win.
Some ringside observers thought Parker, thirty-one, deserved the decision but the Derbyshire fighter endured the second defeat of his 28-bout professional journey.
Buatsi Claims Triumph in Slow Affair
His career development has stalled in recent years through management issues and extended periods of inactivity.
Previously predicted as the future of the British fight scene, he now stands trying to fulfil that early promise - maybe in what feels like a last chance - under recent support.
He began cautiously, with the two boxers ready to take risks in a cagey early stages.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after damaging his hand in the contest, was competing in only his second bout at light-heavyweight.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who utilized a solid defense to edge the cleaner rounds.
The audience's tolerance diminished because of frequent holding, with Parker slipping to the canvas various instances during clinches.
The underdog closed well, but many rounds were difficult to score. Although, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
Buatsi advances, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - on this evidence - still seems difficult.
Hatton Tribute Inspires Manchester Derby Contest
In the secondary fight, Arthur beat Bradley Rea by split-decision in a excellent Manchester vs Manchester fight to secure the European light heavyweight belt.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as 10 bells rang in memory of Manchester's own Hatton, who succumbed 46 years old in recently.
It was the first major televised match card in the location since Hatton's death. As the concluding sound disappeared, the silence transitioned to a chant of "there's only one Hatton".
The action within the ring matched the feeling. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the early round, rising shakily to his feet on the count of eight.
But the traditional red shorts of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was marked up soon, heavy swelling appearing under his orbital area as the fighters landed powerful shots.
The challenger, 27, landed power punches but Arthur, 34, fought fire with fire with powerful upward punches as the pace seldom decreased over the full distance.
Arthur narrowly won the decision with scoring tallies of draw, close margin and clearer margin, but both fighters were determined and full of heart, everything their hero the legend represented.
