British light heavyweight Joshua Buatsi secured a victory yet disappointing beginning to life under recent management with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a tight ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective single shots in a fight where the techniques never quite clicked, with excessive holding spoiling the contest.
Two judges scored it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what defines champions? They succeed," Buatsi commented in the arena as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th pro success.
Several boxing experts thought the challenger, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-match professional journey.
Buatsi Secures Win in Slow Match
Buatsi's progress has slowed in recent years through management issues and considerable time of lack of fights.
Once tipped as the future of UK boxing, he now finds himself trying to fulfil that early promise - maybe in what seems like a last chance - under new promotional backing.
He opened tentatively, with both competitors ready to overcommit in a tentative early stages.
Parker, whose single earlier setback came at the lower weight class against his former opponent in 2022 after suffering a hand injury mid-fight, was competing in only his second fight at light heavyweight.
By the middle rounds, the underdog had made it competitive, causing problems for the favorite, who worked behind a solid defense to narrowly win the better rounds.
The crowd's patience decreased because of regular grabbing, with the challenger falling to the floor multiple occasions during clinches.
Parker finished the stronger, but several stanzas were difficult to score. However, ex-champion Carl Frampton - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
The victor advances, but with the likes of heavy hitter Benavidez, and Russian champion Bivol ruling the division, the path to championship success - based on this performance - still appears challenging.
Ricky Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Lyndon Arthur defeated Rea by divided decision in a outstanding Manchester vs Manchester contest to secure the European light heavyweight title.
The venue fell silent for a profoundly moving memorial prior to the bout as a bell ceremony rang in memory of the city's native Ricky Hatton, who succumbed at age 46 in September.
It was the premier televised fight night in the location since Hatton's passing. As the last bell ended, the silence transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring reflected the sentiment. The eventual winner was sent to the canvas by a left hook squarely on the chin in the second round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. On the opposite side, the opponent - in competitive blue - was marked up soon, significant bruising developing under his orbital area as the fighters traded hard punches.
The challenger, 27, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the intensity hardly diminished over 12 rounds.
The victor narrowly won the decision with scoring tallies of draw, close margin and clearer margin, but the two athletes were relentless and courageous, all the qualities their hero the legend stood for.
