British light heavyweight Buatsi secured a victory yet underwhelming debut to his career under new promoters with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a split decision in a competitive ten-round contest at the boxing arena.
But Parker had his moments, delivering effective single shots in a match where the techniques never quite clicked, with excessive holding disrupting the fight.
The officials scored it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my greatest display but what do champions do? They succeed," the victor said in the ring as he was faced disapproval from the crowd.
The British fighter bounced back after his first professional defeat - an thrilling contest with his previous opponent in February - to earn a twentieth professional win.
Various analysts believed Parker, thirty-one, deserved the victory but the Derbyshire fighter suffered the second setback of his 28-match career.
The Champion Secures Triumph in Uneventful Encounter
Buatsi's progress has slowed in the past few years through promotional disputes and long spells of lack of fights.
Earlier forecast as the future of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what appears to be a last chance - under new promotional backing.
He started carefully, with the two boxers willing to overcommit in a calculated initial rounds.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand in the contest, was participating in his second fight at light-heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the cleaner stanzas.
The spectators' acceptance diminished because of regular grabbing, with Parker falling to the floor multiple occasions during clinches.
Parker ended stronger, but multiple periods were difficult to score. Nevertheless, previous titleholder Carl Frampton - commentating on Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor moves on, but with the presence of heavy hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Homage Inspires Manchester Derby Battle
In the supporting bout, Arthur overcame Rea by divided decision in a outstanding all-Manchester fight to win the continental title.
The venue grew hushed for a extremely emotional tribute prior to the bout as a bell ceremony tolled in honor of local hero Ricky Hatton, who died 46 years old in September.
It was the initial significant broadcast boxing event in the city since the passing of Hatton. As the concluding sound faded, the silence transitioned to a roar of "there's just one Ricky Hatton".
The competition during the bout reflected the emotion. The eventual winner was floored by a left hook flush on the jaw in the early round, rising shakily to his feet on the eight count.
But the red-colored attire of the fighter soon came forward again. From the other corner, the opponent - in rival City blue - was injured quickly, significant bruising appearing under his face as the pair traded punishing blows.
Rea, twenty-seven, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the action hardly diminished over 12 rounds.
Arthur barely secured the verdict with judges scorecards of even score, 115-113 and 115-112, but the two athletes were determined and courageous, everything their idol Hatton stood for.
