British light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under new promoters with a decision win over Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a majority decision in a close ten-round bout at the Co-op Live Arena.
But Parker found success, connecting with powerful clean blows in a contest where the techniques didn't complement each other, with excessive holding marring the fight.
The scoring judges judged it 96-94 for to the winner, with the remaining official a even score.
"It wasn't my best showing but what do champions do? They succeed," Buatsi commented in the ring as he was greeted with disapproval from the crowd.
The Londoner bounced back after his maiden career setback - an memorable fight with Callum Smith in last winter - to secure a 20th pro success.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the contender suffered the second setback of his 28-bout professional journey.
Buatsi Earns Win in Uneventful Match
His career development has slowed in recent years through contract problems and long spells of inactivity.
Earlier forecast as the rising talent of British boxing, he now stands trying to realize his potential - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He began cautiously, with neither fighter willing to take risks in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had kept it close, making life awkward for the favorite, who operated with a solid defense to narrowly win the more effective stanzas.
The crowd's patience diminished during constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
Parker finished the stronger, but multiple periods were hard to judge. Nevertheless, ex-champion Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, giving Buatsi just a single round.
Buatsi advances, but with the presence of power puncher David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires All-Manchester Contest
In the supporting bout, Arthur overcame Rea by divided decision in a terrific local rivalry contest to secure the continental belt.
The venue grew hushed for a extremely emotional homage before the fight as 10 bells sounded in memory of the city's native Hatton, who died aged 46 in September.
It was the premier televised fight night in the city since the passing of Hatton. As the last bell ended, the stillness became a shout of "only one Ricky Hatton".
The action inside the ropes reflected the sentiment. Arthur was knocked down by a significant blow squarely on the face in the early round, getting up unsteadily to his feet on the count of eight.
But the traditional red equipment of the fighter soon advanced again. On the opposite side, Rea - in competitive blue - was marked up soon, significant bruising forming under his eye as the pair landed powerful shots.
The challenger, 27, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over twelve rounds.
Arthur barely secured the verdict with scoring tallies of draw, narrow lead and clearer margin, but each competitor were relentless and courageous, all the qualities their hero the legend embodied.
