UK light-heavyweight Buatsi earned a win yet underwhelming debut to life under new promoters with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a judges' verdict in a tight 10-round bout at the boxing arena.
But the challenger found success, landing some telling clean blows in a match where the styles didn't complement each other, with constant grabbing spoiling the contest.
The scoring judges had it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my greatest showing but what defines champions? They succeed," the victor said in the arena as he was faced negative reactions from the spectators.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a twentieth professional win.
Various analysts felt the challenger, 31, should have been awarded the decision but the contender experienced the second setback of his 28-bout career.
Buatsi Claims Triumph in Slow Encounter
His career development has plateaued in recent times through promotional disputes and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to achieve expectations - perhaps in what feels like a ultimate opportunity - under new promotional backing.
He started carefully, with both competitors ready to overcommit in a tentative opening few rounds.
Parker, 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 the higher weight class.
By the halfway stage, Parker had made it competitive, making life awkward for the favorite, who worked behind a solid defense to barely take the better rounds.
The audience's tolerance decreased amid constant clinching, with Parker going down multiple occasions during clinches.
The underdog ended stronger, but several stanzas were hard to judge. Nevertheless, ex-champion the boxing analyst - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor advances, but with the caliber of power puncher David Benavidez, and Russian champion Bivol ruling the division, the road to world glory - judging by this showing - still appears challenging.
Ricky Hatton Homage Inspires Local Rivalry Fight
In the co-main event, Arthur overcame Bradley Rea by divided decision in a terrific Manchester vs Manchester battle to capture the continental championship.
The stadium grew hushed for a profoundly moving homage before the fight as ten bells rang in remembrance of Manchester's own Hatton, who passed away 46 years old in last month.
It was the initial significant broadcast fight night in the city since the passing of Hatton. As the last bell faded, the stillness transitioned to a shout of "there's just one Ricky Hatton".
The competition during the bout equaled the sentiment. The eventual winner was sent to the canvas by a significant blow flush on the jaw in the second round, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of Arthur soon came forward again. On the opposite side, the opponent - in competitive blue - was damaged early, significant bruising developing under his orbital area as the fighters traded powerful shots.
Rea, twenty-seven, landed power punches but Arthur, 34, responded in kind with powerful upward punches as the pace hardly diminished over twelve rounds.
Arthur narrowly won the verdict with official scores of 114-114, close margin and wider gap, but both fighters were persistent and courageous, exactly what their hero Hatton embodied.
