British light heavyweight Joshua Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a unanimous decision over Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a split decision in a competitive 10-round bout at the Co-op Live Arena.
But Parker landed significant shots, connecting with powerful individual punches in a match where the styles didn't complement each other, with excessive holding marring the contest.
The officials judged it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest showing but what do champions do? They win," Buatsi stated in the ring as he was faced boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in last winter - to secure a 20th pro success.
Some ringside observers believed the challenger, thirty-one, should have been awarded the victory but the contender endured the second defeat of his 28-match career.
The Champion Claims Triumph in Slow Match
Buatsi's progress has plateaued in recent years through management issues and extended periods of lack of fights.
Once tipped as the rising talent of UK boxing, he now stands trying to realize his potential - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to overcommit in a cagey opening few rounds.
The challenger, whose only previous defeat came at the lower weight class against John Ryder in 2022 after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the middle rounds, the underdog had stayed in contention, creating difficulties for the favorite, who operated with a tight guard to barely take the cleaner periods.
The audience's tolerance diminished because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
The underdog closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - providing analysis for Dazn - had it particularly wide for the challenger, giving Buatsi just one round.
The victor progresses, but with the caliber of heavy hitter David Benavidez, and Russian star Bivol dominating the weight class, the path to championship success - on this evidence - still appears challenging.
Ricky Hatton Tribute Motivates Local Rivalry Battle
In the secondary fight, Lyndon Arthur overcame Bradley Rea by split-decision in a excellent local rivalry fight to win the European light-heavyweight championship.
The arena grew hushed for a deeply poignant homage before the fight as 10 bells sounded in remembrance of Manchester's own Ricky Hatton, who succumbed 46 years old in recently.
It was the premier televised boxing event in the city since Hatton's passing. As the concluding sound faded, the silence gave way to a shout of "there's only one Hatton".
The competition during the bout matched the feeling. Arthur was floored by a left hook flush on the jaw in the initial stage, standing uncertainly to his footing on the eight count.
But the Manchester United-red attire of the fighter soon advanced again. Across the ring, the opponent - in competitive blue - was damaged soon, heavy swelling appearing under his face as the fighters landed powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the verdict with official scores of 114-114, close margin and clearer margin, but both fighters were determined and brave, all the qualities their inspiration Hatton embodied.
