UK light heavyweight Joshua Buatsi earned a win yet underwhelming beginning to his career under recent management with a decision win over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a judges' verdict in a close ten-round bout at the Co-op Live Arena.
But the challenger landed significant shots, delivering effective clean blows in a match where the approaches never quite clicked, with excessive holding spoiling the fight.
The officials scored it 96-94 in favor to the winner, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They prevail," the victor commented in the arena as he was faced negative reactions from the audience.
The British fighter returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in last winter - to earn a twentieth professional win.
Several boxing experts thought the challenger, thirty-one, merited the victory but the contender experienced the second loss of his 28-fight professional journey.
The Champion Secures Win in Dull Affair
His career development has stalled in recent times through promotional disputes and long spells of inactivity.
Once tipped as the next star of UK boxing, he now is positioned trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after breaking his hand mid-fight, was participating in his second fight at light-heavyweight.
By the fight's midpoint, Parker had kept it close, creating difficulties for Buatsi, who worked behind a protective stance to narrowly win the more effective stanzas.
The audience's tolerance decreased because of constant clinching, with the challenger slipping to the canvas several times during grappling.
Parker finished the stronger, but several stanzas were challenging to assess. Nevertheless, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for the challenger, scoring for Buatsi just a single round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Tribute Inspires Local Rivalry Battle
In the secondary fight, Lyndon Arthur defeated Bradley Rea by close verdict in a outstanding local rivalry battle to secure the European light heavyweight belt.
The venue fell silent for a profoundly moving tribute prior to the bout as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who passed away 46 years old in September.
It was the first major televised boxing event in the location since Hatton's death. As the concluding sound ended, the silence transitioned to a chant of "there's only one Hatton".
The competition during the bout equaled the emotion. Arthur was floored by a significant blow flush on the jaw in the early round, getting up unsteadily to his position on the count of eight.
But the red-colored equipment of Arthur soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured soon, heavy swelling appearing under his face as the duo exchanged hard punches.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with powerful upward punches as the action seldom decreased over twelve rounds.
The victor barely secured the decision with scoring tallies of even score, narrow lead and wider gap, but the two athletes were relentless and courageous, all the qualities their idol the legend represented.
