British light heavyweight Joshua Buatsi earned a win yet disappointing start to life under recent management with a unanimous decision over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a competitive ten-round bout at the boxing arena.
But the challenger landed significant shots, delivering effective individual punches in a match where the approaches never quite clicked, with excessive holding disrupting the action.
The officials judged it 96-94 to the winner, with the third a 95-95 draw.
"It wasn't my finest display but how do champions respond? They win," the victor stated in the ringside as he was met by negative reactions from the spectators.
The British fighter bounced back after his first professional defeat - an memorable fight with Callum Smith in last winter - to earn a 20th pro success.
Some ringside observers believed the challenger, thirty-one, deserved the decision but the contender suffered the second loss of his 28-bout career.
Buatsi Earns Win in Slow Affair
His career development has slowed in recent years through management issues and considerable time of inactivity.
Once tipped as the next star of British boxing, he now stands trying to fulfil that early promise - maybe in what seems like a final roll of the dice - under recent support.
He opened tentatively, with the two boxers prepared to be aggressive in a cagey opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, making life awkward for Buatsi, who utilized a solid defense to edge the more effective stanzas.
The spectators' acceptance diminished amid regular grabbing, with Parker slipping to the canvas various instances during clinches.
Parker closed well, but several stanzas were challenging to assess. Although, ex-champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just one round.
The victor moves on, but with the presence of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Memorial Motivates Local Rivalry Battle
In the secondary fight, Arthur beat Rea by split-decision in a excellent local rivalry fight to win the European light-heavyweight championship.
The arena became quiet for a deeply poignant tribute ahead of the contest as ten bells rang in honor of Manchester's own Hatton, who died 46 years old in recently.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the concluding sound faded, the quiet became a chant of "there's just one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was sent to the canvas by a left hook squarely on the face in the second round, getting up unsteadily to his position on the referee's count.
But the red-colored attire of the fighter soon came forward again. From the other corner, the opponent - in competitive blue - was damaged quickly, heavy swelling forming under his orbital area as the fighters landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, 34, fought fire with fire with powerful upward punches as the action seldom decreased over twelve rounds.
Arthur edged the result with scoring tallies of 114-114, narrow lead and 115-112, but both fighters were persistent and courageous, all the qualities their hero Hatton stood for.
