British light-heavyweight Joshua Buatsi secured a victory yet underwhelming beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a judges' verdict in a close ten-round contest at the boxing arena.
But the challenger landed significant shots, delivering effective individual punches in a fight where the styles never quite clicked, with excessive holding marring the fight.
The scoring judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what do champions do? They prevail," Buatsi stated in the arena as he was greeted with boos from the crowd.
The British fighter bounced back after his maiden career setback - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought the challenger, 31, merited the decision but the Derbyshire fighter experienced the second setback of his 28-match professional journey.
Buatsi Claims Triumph in Slow Match
The fighter's advancement has plateaued in the past few years through management issues and long spells of lack of fights.
Once tipped as the next star of UK boxing, he now finds himself trying to realize his potential - perhaps in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with neither fighter willing to take risks in a cagey initial rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had made it competitive, making life awkward for the favorite, who operated with a solid defense to narrowly win the more effective periods.
The audience's tolerance diminished because of constant clinching, with Parker falling to the floor several times during close exchanges.
Parker ended stronger, but multiple periods were hard to judge. Nevertheless, former world champion the boxing analyst - working with Dazn - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter Benavidez, and Eastern European fighter Bivol ruling the division, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Fuels Manchester Derby Contest
In the supporting bout, Lyndon Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester fight to win the continental championship.
The arena grew hushed for a profoundly moving tribute prior to the bout as 10 bells sounded in honor of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the first major televised match card in the location since Hatton's passing. As the last bell faded, the silence became a chant of "only one Hatton".
The competition within the ring matched the feeling. The eventual winner was floored by a left hook flush on the face in the initial stage, getting up unsteadily to his footing on the count of eight.
But the red-colored equipment of the fighter soon advanced again. From the other corner, Rea - in rival City blue - was damaged early, heavy swelling developing under his eye as the fighters landed punishing blows.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with powerful upward punches as the intensity hardly diminished over twelve rounds.
Arthur narrowly won the result with official scores of 114-114, narrow lead and wider gap, but the two athletes were persistent and brave, exactly what their inspiration Hatton stood for.
