British light heavyweight Joshua Buatsi made a winning yet disappointing debut to life under recent management with a points victory over Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a judges' verdict in a close ten-round fight at the Manchester venue.
But the challenger had his moments, delivering effective individual punches in a fight where the approaches failed to mesh, with excessive holding marring the contest.
The officials judged it 96-94 for to the winner, with the third a even score.
"It wasn't my finest performance but how do champions respond? They win," the victor said in the arena as he was faced negative reactions from the crowd.
The British fighter bounced back after his first professional defeat - an thrilling contest with Callum Smith in last winter - to claim a twentieth professional win.
Various analysts thought Parker, thirty-one, merited the win but the contender endured the second setback of his 28-bout professional journey.
Buatsi Earns Triumph in Uneventful Encounter
The fighter's advancement has slowed in recent times through contract problems and considerable time of lack of fights.
Earlier forecast as the future of UK 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 neither fighter ready to take risks in a calculated opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in 2022 after damaging his hand during the bout, was participating in his second bout at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, causing problems for the favorite, who operated with a protective stance to edge the more effective rounds.
The spectators' acceptance wore thin because of constant clinching, with the challenger slipping to the canvas various instances during grappling.
Parker closed well, but many rounds were challenging to assess. Although, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it strongly leaning for Parker, giving Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter David Benavidez, and Russian star Bivol dominating the weight class, the journey to titles - judging by this showing - still appears challenging.
Hatton Tribute Inspires All-Manchester Fight
In the secondary fight, Arthur overcame Rea by split-decision in a outstanding Manchester vs Manchester fight to secure the continental belt.
The arena became quiet for a profoundly moving memorial ahead of the contest as 10 bells tolled in honor of Manchester's own Ricky Hatton, who succumbed 46 years old in September.
It was the initial significant broadcast fight night in the urban center since the passing of Hatton. As the last bell ended, the silence became a shout of "only one Ricky Hatton".
The action inside the ropes equaled the feeling. Arthur was floored by a significant blow squarely on the jaw in the initial stage, getting up unsteadily to his position on the referee's count.
But the red-colored attire of the fighter soon advanced again. Across the ring, Rea - in competitive blue - was marked up quickly, noticeable damage developing under his eye as the pair exchanged punishing blows.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the action hardly diminished over twelve rounds.
Arthur narrowly won the result with scoring tallies of even score, narrow lead and clearer margin, but both fighters were determined and full of heart, exactly what their inspiration the legend represented.
