British light heavyweight Joshua Buatsi earned a win yet underwhelming debut to his career under new promoters with a points victory over Parker in the Manchester arena.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a competitive 10-round fight at the Manchester venue.
But the challenger had his moments, connecting with powerful individual punches in a match where the styles never quite clicked, with constant grabbing marring the fight.
Two judges had it 96-94 for to Buatsi, with the third a even score.
"It wasn't my best display but what defines champions? They win," Buatsi stated in the arena as he was faced boos from the spectators.
The Londoner returned to winning ways after his maiden career setback - an memorable fight with Callum Smith in last winter - to earn a 20th career victory.
Several boxing experts thought Parker, thirty-one, deserved the win but the contender endured the second setback of his 28-match professional journey.
The Champion Claims Victory in Dull Match
His career development has stalled in recent years through management issues and extended periods 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 final roll of the dice - under fresh management.
He opened tentatively, with both competitors willing to take risks in a calculated opening few rounds.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was competing in only his second fight at light heavyweight.
By the middle rounds, Parker had stayed in contention, causing problems for the favorite, who worked behind a solid defense to edge the more effective rounds.
The audience's tolerance decreased amid constant clinching, with the challenger slipping to the canvas several times during close exchanges.
The underdog finished the stronger, but several stanzas were challenging to assess. Nevertheless, previous titleholder the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just a single round.
The victor advances, but with the caliber of hard hitter Benavidez, and Russian champion Bivol dominating the weight class, the path to championship success - based on this performance - still seems difficult.
Hatton Memorial Inspires All-Manchester Fight
In the co-main event, Arthur beat Rea by divided decision in a terrific all-Manchester contest to secure the European light-heavyweight title.
The venue became quiet for a profoundly moving tribute ahead of the contest as ten bells rang in remembrance of local hero Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast match card in the city since Hatton's passing. As the final chime faded, the stillness transitioned to a chant of "there's just one Ricky Hatton".
The competition inside the ropes matched the sentiment. The eventual winner was floored by a left hook directly to the face in the second round, rising shakily to his position on the referee's count.
But the red-colored shorts of the fighter soon came forward again. Across the ring, Rea - in opposing blue - was damaged quickly, noticeable damage appearing under his eye as the duo exchanged powerful shots.
The challenger, twenty-seven, connected with strong blows but the champion, thirty-four, responded in kind with powerful upward punches as the intensity seldom decreased over the full distance.
Arthur narrowly won the result with judges scorecards of 114-114, 115-113 and wider gap, but the two athletes were determined and full of heart, exactly what their inspiration the legend stood for.
