UK light heavyweight Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a majority decision in a close 10-round contest at the Co-op Live Arena.
But Parker had his moments, delivering effective single shots in a fight where the styles never quite clicked, with excessive holding marring the fight.
The officials judged it 96-94 for to the winner, with the final judge a even score.
"It wasn't my greatest display but how do champions respond? They prevail," the victor said in the arena as he was met by boos from the audience.
The Londoner returned to winning ways after his first professional defeat - an epic battle with his previous opponent in February - to secure a twentieth professional win.
Several boxing experts believed the challenger, 31, merited the decision but the British boxer experienced the second defeat of his 28-match career.
Buatsi Secures Victory in Uneventful Match
His career development has stalled in recent years through promotional disputes and extended periods of inactivity.
Once tipped as the future of the British fight scene, he now finds himself trying to fulfil that early promise - possibly in what seems like a ultimate opportunity - under recent support.
He opened tentatively, with neither fighter ready to take risks in a calculated opening few rounds.
Parker, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand during the bout, was making just his second bout at light-heavyweight.
By the fight's midpoint, the underdog had made it competitive, causing problems for Buatsi, who operated with a tight guard to barely take the more effective rounds.
The audience's tolerance decreased during frequent holding, with Parker going down various instances during clinches.
The underdog finished the stronger, but several stanzas were difficult to score. Although, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for Parker, awarding Buatsi just only one stanza.
Buatsi advances, but with the presence of hard hitter David Benavidez, and Eastern European fighter Bivol leading the category, the road to world glory - judging by this showing - still looks steep.
Hatton Homage Inspires All-Manchester Battle
In the supporting bout, Arthur defeated Rea by divided decision in a outstanding all-Manchester battle to capture the continental belt.
The arena fell silent for a deeply poignant homage ahead of the contest as 10 bells tolled in memory of local hero Ricky Hatton, who succumbed at age 46 in last month.
It was the premier televised fight night in the urban center since the passing of Hatton. As the concluding sound disappeared, the quiet transitioned to a shout of "there's just one Hatton".
The action within the ring equaled the emotion. The eventual winner was floored by a significant blow flush on the chin in the early round, getting up unsteadily to his footing on the eight count.
But the Manchester United-red attire of the fighter soon came forward again. Across the ring, the opponent - in opposing blue - was marked up early, heavy swelling developing under his face as the fighters exchanged punishing blows.
Rea, 27, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the action seldom decreased over twelve rounds.
The victor barely secured the result with judges scorecards of even score, 115-113 and clearer margin, but each competitor were relentless and brave, all the qualities their inspiration the legend stood for.
