UK light-heavyweight Joshua Buatsi made a winning yet underwhelming debut to life under recent management with a decision win over Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight ten-round bout at the Manchester venue.
But the challenger landed significant shots, landing some telling single shots in a match where the techniques failed to mesh, with frequent clinching marring the contest.
The officials judged it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my finest showing but how do champions respond? They prevail," Buatsi commented in the ring as he was faced negative reactions from the spectators.
The British fighter got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to earn a twentieth professional win.
Various analysts felt Parker, 31, deserved the win but the Derbyshire fighter experienced the second defeat of his 28-bout professional journey.
Buatsi Earns Win in Dull Affair
The fighter's advancement has stalled in recent years through contract problems and long spells of inactivity.
Previously predicted as the rising talent of British boxing, he now stands trying to fulfil that early promise - possibly in what appears to be a last chance - under recent support.
He started carefully, with both competitors willing to take risks in a calculated initial rounds.
Parker, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand during the bout, was making just his second bout at the higher weight class.
By the fight's midpoint, Parker had made it competitive, creating difficulties for the favorite, who operated with a tight guard to barely take the more effective periods.
The audience's tolerance diminished because of constant clinching, with the challenger slipping to the canvas several times during clinches.
The underdog ended stronger, but many rounds were challenging to assess. However, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just one round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Tribute Motivates Local Rivalry Battle
In the supporting bout, Arthur defeated Rea by close verdict in a excellent all-Manchester battle to secure the European light-heavyweight title.
The venue fell silent for a deeply poignant memorial ahead of the contest as a bell ceremony tolled in honor of Manchester's own Hatton, who passed away 46 years old in September.
It was the initial significant broadcast boxing event in the city since Hatton's passing. As the concluding sound faded, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The competition inside the ropes matched the emotion. Arthur was knocked down by a significant blow flush on the chin in the second round, rising shakily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was injured early, significant bruising developing under his face as the pair traded powerful shots.
The challenger, 27, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace rarely dropped over 12 rounds.
Arthur barely secured the decision with scoring tallies of even score, close margin and 115-112, but the two athletes were relentless and brave, exactly what their inspiration Hatton represented.
