UK light heavyweight Buatsi earned a win yet underwhelming beginning to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a split decision in a tight ten-round fight at the Co-op Live Arena.
But Parker found success, delivering effective individual punches in a fight where the approaches failed to mesh, with constant grabbing spoiling the contest.
Two judges judged it 96-94 in favor to the winner, with the remaining official a 95-95 draw.
"It wasn't my finest showing but what defines champions? They win," Buatsi commented in the arena as he was met by boos from the spectators.
The Londoner returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to claim a 20th pro success.
Some ringside observers felt the challenger, 31, deserved the win but the British boxer experienced the second setback of his 28-match professional journey.
The Champion Secures Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent times through contract problems and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now stands trying to fulfil that early promise - possibly in what seems like a last chance - under recent support.
He opened tentatively, with both competitors willing to be aggressive in a calculated early stages.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after breaking his hand during the bout, was making just his second bout at light heavyweight.
By the middle rounds, the underdog had stayed in contention, causing problems for the favorite, who utilized a solid defense to narrowly win the better periods.
The spectators' acceptance wore thin because of regular grabbing, with Parker going down various instances during clinches.
Parker closed well, but multiple periods were challenging to assess. Nevertheless, ex-champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, giving Buatsi just a single round.
The victor moves on, but with the caliber of hard hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - on this evidence - still looks steep.
Ricky Hatton Homage Motivates All-Manchester Fight
In the supporting bout, Arthur overcame Bradley Rea by divided decision in a excellent all-Manchester fight to capture the European light heavyweight belt.
The venue grew hushed for a extremely emotional memorial ahead of the contest as 10 bells rang in honor of Manchester's own Ricky Hatton, who died aged 46 in recently.
It was the first major televised match card in the location since Hatton's death. As the final chime ended, the silence became a chant of "there's only one Ricky Hatton".
The action during the bout equaled the feeling. The eventual winner was knocked down by a significant blow flush on the face in the initial stage, rising shakily to his feet on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. On the opposite side, the opponent - in opposing blue - was injured soon, noticeable damage developing under his orbital area as the duo traded powerful shots.
Rea, twenty-seven, delivered effective strikes but Arthur, 34, responded in kind with powerful upward punches as the action hardly diminished over the full distance.
Arthur barely secured the result with official scores of even score, narrow lead and clearer margin, but the two athletes were determined and courageous, exactly what their idol Hatton stood for.
