British light-heavyweight Joshua Buatsi earned a win yet underwhelming start to his career under fresh promotional backing with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's work rate seemingly secured him a split decision in a tight ten-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a match where the techniques failed to mesh, with excessive holding disrupting the action.
The scoring judges judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but what do champions do? They succeed," Buatsi stated in the ring as he was faced disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts believed the challenger, thirty-one, deserved the victory but the Derbyshire fighter suffered the second defeat of his 28-fight professional journey.
The Champion Secures Triumph in Uneventful Encounter
The fighter's advancement has plateaued in the past few years through management issues and extended periods of inactivity.
Previously predicted as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what seems like a last chance - under recent support.
He started carefully, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in two years ago after suffering a hand injury mid-fight, was competing in only his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, making life awkward for Buatsi, who worked behind a tight guard to edge the better periods.
The crowd's patience wore thin because of constant clinching, with the challenger slipping to the canvas several times during close exchanges.
The underdog closed well, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - working with the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just a single round.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian champion Dmitry Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Hatton Memorial Inspires Local Rivalry Contest
In the co-main event, Arthur beat Bradley Rea by divided decision in a excellent local rivalry battle to capture the continental title.
The stadium became quiet for a profoundly moving homage before the fight as 10 bells tolled in honor of local hero Hatton, who passed away aged 46 in September.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the concluding sound ended, the quiet became a roar of "there's just one Ricky Hatton".
The competition during the bout matched the feeling. Arthur was sent to the canvas by a powerful punch squarely on the face in the second round, rising shakily to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon came forward again. From the other corner, the opponent - in competitive blue - was injured early, heavy swelling developing under his eye as the duo exchanged punishing blows.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity seldom decreased over twelve rounds.
Arthur barely secured the result with official scores of draw, narrow lead and clearer margin, but both fighters were determined and courageous, all the qualities their hero Hatton represented.
