British light heavyweight Joshua Buatsi made a winning yet unimpressive debut to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level seemingly secured him a split decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger found success, delivering effective single shots in a contest where the styles never quite clicked, with excessive holding disrupting the contest.
The scoring judges judged it 96-94 to the winner, with the final judge a 95-95 draw.
"It wasn't my best showing but what defines champions? They succeed," the victor said in the arena as he was faced disapproval from the audience.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to earn a 20th pro success.
Some ringside observers felt Parker, 31, should have been awarded the win but the British boxer experienced the second defeat of his 28-bout professional journey.
The Champion Claims Win in Uneventful Affair
His career development has slowed in the past few years through management issues and extended periods of lack of fights.
Once tipped as the next star of the British fight scene, he now finds himself trying to realize his potential - maybe in what appears to be a last chance - under recent support.
He started carefully, with the two boxers willing to be aggressive in a tentative initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury during the bout, was competing in only his second fight at light-heavyweight.
By the middle rounds, Parker had kept it close, making life awkward for Buatsi, who utilized a solid defense to barely take the better stanzas.
The spectators' acceptance decreased during frequent holding, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were hard to judge. However, ex-champion Carl Frampton - commentating on Dazn - had it significantly in favor for Parker, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still appears challenging.
Hatton Memorial Motivates All-Manchester Contest
In the co-main event, Arthur beat Bradley Rea by close verdict in a outstanding all-Manchester contest to capture the European light-heavyweight belt.
The venue became quiet for a profoundly moving memorial ahead of the contest as a bell ceremony sounded in remembrance of local hero Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast match card in the urban center since Hatton's death. As the last bell disappeared, the stillness gave way to a chant of "there's just one Hatton".
The action during the bout matched the feeling. Arthur was sent to the canvas by a left hook flush on the chin in the second round, getting up unsteadily to his position on the referee's count.
But the traditional red equipment of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was damaged early, significant bruising forming under his orbital area as the pair traded powerful shots.
The challenger, 27, landed power punches but Arthur, 34, matched the intensity with effective uppercuts as the pace rarely dropped over the full distance.
The victor narrowly won the result with judges scorecards of even score, narrow lead and wider gap, but the two athletes were relentless and brave, everything their hero Hatton embodied.
