British light heavyweight Joshua Buatsi secured a victory yet disappointing start to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic medal winner's activity level appeared to earn him a split decision in a competitive ten-round fight at the boxing arena.
But Parker landed significant shots, delivering effective single shots in a fight where the approaches didn't complement each other, with constant grabbing disrupting the fight.
The officials had it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest display but what do champions do? They succeed," the victor stated in the ringside as he was faced boos from the audience.
The British fighter bounced back after his maiden career setback - an thrilling contest with his previous opponent in February - to earn a 20th career victory.
Some ringside observers believed the challenger, 31, merited the victory but the contender endured the second defeat of his 28-fight professional journey.
The Champion Claims Victory in Uneventful Match
The fighter's advancement has slowed in the past few years through management issues and long spells of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - possibly in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with the two boxers willing to be aggressive in a cagey early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand in the contest, was competing in only his second appearance at the higher weight class.
By the fight's midpoint, Parker had kept it close, creating difficulties for Buatsi, who worked behind a solid defense to edge the cleaner rounds.
The crowd's patience decreased because of frequent holding, with the challenger slipping to the canvas several times during grappling.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion Carl Frampton - working with the broadcast network - had it strongly leaning for the challenger, giving Buatsi just one round.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Motivates Local Rivalry Fight
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a outstanding local rivalry battle to secure the European light heavyweight title.
The venue grew hushed for a profoundly moving homage before the fight as 10 bells tolled in honor of local hero Ricky Hatton, who died at age 46 in September.
It was the first major televised fight night in the city since Hatton's death. As the last bell ended, the quiet transitioned to a shout of "only one Ricky Hatton".
The action within the ring reflected the feeling. Arthur was floored by a powerful punch flush on the jaw in the early round, rising shakily to his footing on the count of eight.
But the Manchester United-red shorts of the fighter soon advanced again. Across the ring, the opponent - in rival City blue - was injured quickly, noticeable damage forming under his eye as the fighters exchanged powerful shots.
Rea, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over the full distance.
Arthur barely secured the result with judges scorecards of 114-114, close margin and clearer margin, but each competitor were relentless and full of heart, everything their inspiration Hatton stood for.
