British light heavyweight Joshua Buatsi earned a win yet unimpressive start to life under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close ten-round fight at the Co-op Live Arena.
But the challenger had his moments, landing some telling individual punches in a match where the styles didn't complement each other, with frequent clinching disrupting the action.
Two judges scored it 96-94 for to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest display but how do champions respond? They prevail," Buatsi said in the ring as he was faced disapproval from the crowd.
The Londoner bounced back after his initial pro loss - an thrilling contest with his previous opponent in February - to secure a 20th career victory.
Some ringside observers believed the challenger, thirty-one, merited the decision but the contender endured the second defeat of his 28-fight career.
Buatsi Earns Triumph in Slow Encounter
His career development has slowed in the past few years through management issues and considerable time of inactivity.
Previously predicted as the future of the British fight scene, he now finds himself trying to achieve expectations - possibly in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with neither fighter prepared to be aggressive in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after breaking his hand in the contest, was making just his second fight at the higher weight class.
By the halfway stage, the underdog had made it competitive, causing problems for the favorite, who utilized a tight guard to narrowly win the cleaner stanzas.
The crowd's patience wore thin during frequent holding, with Parker going down various instances during clinches.
Parker finished the stronger, but several stanzas were difficult to score. Nevertheless, ex-champion Carl Frampton - commentating on the broadcast network - had it significantly in favor for Parker, giving Buatsi just one round.
Buatsi moves on, but with the presence of power puncher David Benavidez, and Russian champion Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Ricky Hatton Memorial Fuels Local Rivalry Fight
In the co-main event, Arthur beat Rea by divided decision in a excellent Manchester vs Manchester fight to secure the continental championship.
The venue grew hushed for a profoundly moving homage prior to the bout as a bell ceremony rang in honor of local hero Ricky Hatton, who passed away at age 46 in last month.
It was the initial significant broadcast fight night in the urban center since Hatton's passing. As the concluding sound ended, the quiet became a shout of "there's just one Hatton".
The fighting during the bout reflected the sentiment. The eventual winner was sent to the canvas by a powerful punch squarely on the face in the early round, standing uncertainly to his position on the count of eight.
But the red-colored attire of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was damaged quickly, heavy swelling developing under his orbital area as the duo landed punishing blows.
The challenger, 27, connected with strong blows but Arthur, 34, matched the intensity with powerful upward punches as the pace hardly diminished over 12 rounds.
Arthur edged the verdict with judges scorecards of even score, narrow lead and clearer margin, but the two athletes were persistent and courageous, exactly what their inspiration Hatton embodied.
