British light heavyweight Joshua Buatsi made a winning yet underwhelming beginning to his career under new promoters with a unanimous decision over Parker in Manchester.
The Olympic medal winner's activity level appeared to earn him a majority decision in a competitive 10-round bout at the Manchester venue.
But the challenger found success, connecting with powerful single shots in a contest where the techniques failed to mesh, with constant grabbing disrupting the action.
The officials had it 96-94 to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest display but how do champions respond? They succeed," Buatsi stated in the ring as he was greeted with disapproval from the spectators.
The Londoner returned to winning ways after his initial pro loss - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Some ringside observers thought the challenger, thirty-one, deserved the decision but the Derbyshire fighter suffered the second loss of his 28-bout career.
Buatsi Secures Win in Slow Affair
His career development has stalled in recent times through promotional disputes and considerable time of inactivity.
Once tipped as the future of British boxing, he now finds himself trying to achieve expectations - maybe in what feels like a ultimate opportunity - under fresh management.
He started carefully, with both competitors willing to take risks in a calculated initial rounds.
Parker, whose only previous defeat came at the lower weight class against John Ryder in 2022 after damaging his hand during the bout, was making just his second appearance at light-heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who operated with a tight guard to edge the more effective rounds.
The spectators' acceptance diminished amid frequent holding, with the challenger going down multiple occasions during close exchanges.
Parker ended stronger, but multiple periods were difficult to score. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - on this evidence - still looks steep.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by split-decision in a excellent local rivalry fight to secure the European light heavyweight title.
The stadium grew hushed for a profoundly moving memorial ahead of the contest as ten bells tolled in memory of local hero Hatton, who passed away at age 46 in last month.
It was the premier televised fight night in the location since the passing of Hatton. As the last bell ended, the stillness became a roar of "there's only one Hatton".
The action inside the ropes reflected the sentiment. Arthur was floored by a significant blow flush on the jaw in the second round, standing uncertainly to his feet on the count of eight.
But the traditional red shorts of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was marked up quickly, noticeable damage appearing under his face as the pair landed hard punches.
Rea, 27, connected with strong blows but Arthur, thirty-four, matched the intensity with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor edged the result with official scores of draw, 115-113 and clearer margin, but both fighters were determined and brave, exactly what their inspiration the legend stood for.
