UK light heavyweight Buatsi secured a victory yet underwhelming start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a majority decision in a competitive 10-round fight at the boxing arena.
But the challenger landed significant shots, connecting with powerful individual punches in a contest where the styles never quite clicked, with constant grabbing disrupting the contest.
The scoring judges scored it 96-94 for to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest display but what defines champions? They succeed," Buatsi stated in the ring as he was faced boos from the spectators.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to secure a 20th career victory.
Some ringside observers thought Parker, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second loss of his 28-bout career.
The Champion Claims Victory in Uneventful Encounter
The fighter's advancement has plateaued in recent years through management issues and extended periods of lack of fights.
Earlier forecast as the next star of the British fight scene, he now finds himself trying to realize his potential - perhaps in what appears to be a final roll of the dice - under fresh management.
He began cautiously, with both competitors prepared to take risks in a tentative opening few rounds.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was competing in only his second bout at light heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who worked behind a protective stance to narrowly win the better stanzas.
The spectators' acceptance wore thin amid constant clinching, with the challenger falling to the floor several times during clinches.
The underdog closed well, but several stanzas were challenging to assess. However, former world champion the boxing analyst - commentating on Dazn - had it significantly in favor for Parker, awarding Buatsi just a single round.
The victor moves on, but with the likes of power puncher David Benavidez, and Russian champion Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires Manchester Derby Battle
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to win the continental belt.
The arena became quiet for a profoundly moving tribute prior to the bout as a bell ceremony tolled in remembrance of local hero Ricky Hatton, who passed away at age 46 in September.
It was the initial significant broadcast boxing event in the location since Hatton's passing. As the concluding sound disappeared, the quiet transitioned to a shout of "only one Ricky Hatton".
The action during the bout matched the feeling. The eventual winner was floored by a significant blow directly to the face in the initial stage, rising shakily to his position on the referee's count.
But the red-colored shorts of Arthur soon pressed ahead again. Across the ring, Rea - in rival City blue - was injured soon, noticeable damage developing under his face as the pair landed punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, responded in kind with powerful upward punches as the pace hardly diminished over 12 rounds.
Arthur barely secured the verdict with official scores of draw, narrow lead and clearer margin, but the two athletes were persistent and courageous, exactly what their hero Hatton represented.
