UK light heavyweight Buatsi earned a win yet disappointing beginning to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's work rate seemingly secured him a majority decision in a competitive 10-round fight at the Manchester venue.
But Parker landed significant shots, landing some telling clean blows in a fight where the techniques never quite clicked, with constant grabbing disrupting the action.
Two judges scored it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my finest showing but what defines champions? They win," the victor stated in the ring as he was faced negative reactions from the crowd.
The Londoner returned to winning ways after his maiden career setback - an epic battle with his previous opponent in February - to claim a 20th career victory.
Several boxing experts believed Parker, thirty-one, should have been awarded the victory but the British boxer endured the second defeat of his 28-fight career.
The Champion Earns Triumph in Uneventful Encounter
The fighter's advancement has stalled in recent times through contract problems and long spells of lack of fights.
Previously predicted as the next star 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 both competitors ready to take risks in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second appearance at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a tight guard to barely take the cleaner periods.
The spectators' acceptance decreased because of regular grabbing, with the challenger falling to the floor several times during grappling.
Parker finished the stronger, but many rounds were hard to judge. However, previous titleholder Carl Frampton - providing analysis for Dazn - had it strongly leaning for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - on this evidence - still seems difficult.
Hatton Homage Fuels All-Manchester Battle
In the supporting bout, Arthur overcame Rea by close verdict in a excellent all-Manchester contest to capture the continental belt.
The arena grew hushed for a extremely emotional tribute ahead of the contest as ten bells rang in remembrance of the city's native Hatton, who died 46 years old in recently.
It was the first major televised boxing event in the urban center since the passing of Hatton. As the last bell faded, the silence transitioned to a chant of "only one Ricky Hatton".
The competition inside the ropes reflected the sentiment. The eventual winner was knocked down by a left hook flush on the face in the early round, standing uncertainly to his feet on the referee's count.
But the red-colored equipment of Arthur soon pressed ahead again. From the other corner, the opponent - in rival City blue - was damaged soon, significant bruising appearing under his eye as the fighters exchanged punishing blows.
Rea, twenty-seven, landed power punches but Arthur, 34, fought fire with fire with effective uppercuts as the pace rarely dropped over the full distance.
Arthur barely secured the result with scoring tallies of draw, close margin and wider gap, but each competitor were persistent and courageous, everything their idol Hatton represented.
