British light-heavyweight Buatsi made a winning yet disappointing beginning to his career under new promoters with a decision win over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a split decision in a tight ten-round bout at the Manchester venue.
But Parker found success, delivering effective single shots in a match where the styles never quite clicked, with constant grabbing marring the action.
Two judges scored it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my greatest performance but what defines champions? They win," Buatsi stated in the ringside as he was greeted with negative reactions from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in February - to secure a 20th pro success.
Various analysts believed Parker, thirty-one, should have been awarded the victory but the British boxer experienced the second setback of his 28-fight professional journey.
Buatsi Secures Victory in Uneventful Encounter
The fighter's advancement has plateaued in the past few years through promotional disputes and long spells of lack of fights.
Previously predicted as the future of the British fight scene, he now finds himself trying to realize his potential - perhaps in what seems like a last chance - under new promotional backing.
He started carefully, with neither fighter ready to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after breaking his hand mid-fight, was participating in his second appearance at light-heavyweight.
By the halfway stage, Parker had kept it close, creating difficulties for Buatsi, who worked behind a solid defense to barely take the better periods.
The audience's tolerance wore thin because of regular grabbing, with Parker falling to the floor several times during grappling.
The underdog closed well, but multiple periods were difficult to score. Nevertheless, former world champion the boxing analyst - commentating on Dazn - had it strongly leaning for the challenger, giving Buatsi just a single round.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol leading the category, the path to championship success - judging by this showing - still appears challenging.
Hatton Homage Inspires Local Rivalry Battle
In the supporting bout, Arthur beat Rea by split-decision in a outstanding all-Manchester fight to secure the continental belt.
The arena became quiet for a deeply poignant tribute ahead of the contest as 10 bells sounded in honor of Manchester's own Hatton, who succumbed 46 years old in recently.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the concluding sound faded, the quiet transitioned to a shout of "there's just one Ricky Hatton".
The action within the ring equaled the feeling. Arthur was sent to the canvas by a powerful punch directly to the face in the initial stage, rising shakily to his footing on the eight count.
But the Manchester United-red equipment of the fighter soon came forward again. On the opposite side, Rea - in opposing blue - was marked up quickly, significant bruising appearing under his eye as the pair landed powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, fought fire with fire with powerful upward punches as the pace seldom decreased over 12 rounds.
Arthur barely secured the result with judges scorecards of 114-114, close margin and clearer margin, but the two athletes were persistent and courageous, exactly what their idol Hatton embodied.
