UK light-heavyweight Buatsi earned a win yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's punch output seemingly secured him a majority decision in a tight 10-round fight at the boxing arena.
But Parker landed significant shots, delivering effective single shots in a match where the approaches failed to mesh, with excessive holding disrupting the action.
The officials had it 96-94 in favor to Buatsi, with the remaining official a 95-95 draw.
"It wasn't my finest performance but what defines champions? They succeed," Buatsi commented in the arena as he was met by boos from the spectators.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in last winter - to claim a 20th career victory.
Several boxing experts felt the challenger, thirty-one, deserved the decision but the British boxer endured the second defeat of his 28-match professional journey.
Buatsi Secures Win in Dull Affair
Buatsi's progress has stalled in recent years through contract problems and extended periods of inactivity.
Once tipped as the next star of British boxing, he now is positioned trying to realize his potential - possibly in what feels like a final roll of the dice - under recent support.
He began cautiously, with neither fighter willing to overcommit in a tentative initial rounds.
The challenger, whose single earlier setback came at super-middleweight against his former opponent in 2022 after suffering a hand injury in the contest, was participating in his second appearance at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, creating difficulties for Buatsi, who operated with a solid defense to edge the cleaner periods.
The audience's tolerance wore thin because of regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog closed well, but several stanzas were difficult to score. However, former world champion the boxing analyst - providing analysis for the broadcast network - had it strongly leaning for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the caliber of heavy hitter David Benavidez, and Russian star Dmitry Bivol leading the category, the journey to titles - judging by this showing - still seems difficult.
Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Arthur defeated Bradley Rea by close verdict in a outstanding Manchester vs Manchester contest to capture the European light-heavyweight championship.
The arena became quiet for a profoundly moving memorial before the fight as a bell ceremony tolled in honor of the city's native Ricky Hatton, who succumbed 46 years old in September.
It was the premier televised match card in the city since the passing of Hatton. As the final chime ended, the silence gave way to a roar of "there's just one Ricky Hatton".
The competition inside the ropes equaled the feeling. Arthur was knocked down by a powerful punch flush on the face in the initial stage, getting up unsteadily to his footing on the referee's count.
But the red-colored equipment of the fighter soon came forward again. On the opposite side, the opponent - in opposing blue - was damaged early, noticeable damage appearing under his eye as the duo exchanged hard punches.
The challenger, twenty-seven, connected with strong blows but Arthur, 34, matched the intensity with stinging uppercuts as the pace hardly diminished over 12 rounds.
Arthur edged the verdict with scoring tallies of even score, 115-113 and 115-112, but both fighters were relentless and brave, all the qualities their idol the legend embodied.
