British 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 medal winner's work rate likely gained him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker landed significant shots, connecting with powerful clean blows in a fight where the styles never quite clicked, with excessive holding disrupting the contest.
Two judges judged it 96-94 for to Buatsi, with the third a 95-95 draw.
"It wasn't my greatest performance but what do champions do? They win," the victor stated in the arena as he was faced boos from the crowd.
The Londoner bounced back after his maiden career setback - an thrilling contest with his previous opponent in last winter - to earn a twentieth professional win.
Some ringside observers believed Parker, 31, deserved the win but the British boxer endured the second setback of his 28-match professional journey.
The Champion Claims Victory in Dull Encounter
The fighter's advancement has stalled in the past few years through promotional disputes and extended periods of inactivity.
Earlier forecast as the rising talent of the British fight scene, he now stands trying to achieve expectations - maybe in what appears to be a final roll of the dice - under recent support.
He began cautiously, with both competitors prepared to be aggressive in a calculated opening few rounds.
Parker, whose single earlier setback came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was competing in only his second bout at light heavyweight.
By the halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who worked behind a solid defense to narrowly win the more effective rounds.
The spectators' acceptance wore thin because of regular grabbing, with the challenger slipping to the canvas several times during grappling.
Parker finished the stronger, but multiple periods were difficult to score. Although, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just a single round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the road to world glory - based on this performance - still seems difficult.
Ricky Hatton Tribute Fuels All-Manchester Battle
In the co-main event, Arthur beat Bradley Rea by close verdict in a terrific Manchester vs Manchester battle to capture the European light heavyweight title.
The arena grew hushed for a extremely emotional homage ahead of the contest as a bell ceremony sounded in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the premier televised boxing event in the location since the passing of Hatton. As the last bell faded, the silence gave way to a roar of "there's just one Ricky Hatton".
The competition within the ring reflected the emotion. Arthur was knocked down by a significant blow directly to the face in the second round, getting up unsteadily to his feet on the eight count.
But the red-colored attire of the fighter soon advanced again. On the opposite side, the opponent - in rival City blue - was damaged quickly, noticeable damage developing under his orbital area as the fighters landed powerful shots.
Rea, 27, delivered effective strikes but Arthur, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over the full distance.
Arthur narrowly won the decision with judges scorecards of even score, 115-113 and wider gap, but both fighters were relentless and full of heart, everything their idol Hatton stood for.
