British light heavyweight Buatsi made a winning yet underwhelming start to life under fresh promotional backing with a decision win over Zach Parker in Manchester.
The Olympic bronze medallist's activity level likely gained him a judges' verdict in a competitive 10-round fight at the Co-op Live Arena.
But the challenger landed significant shots, landing some telling clean blows in a match where the styles failed to mesh, with excessive holding marring the fight.
Two judges judged it 96-94 to the winner, with the third a even score.
"It wasn't my greatest display but what defines champions? They win," the victor commented in the ring as he was greeted with negative reactions from the spectators.
The British fighter bounced back after his initial pro loss - an epic battle with his previous opponent in February - to earn a 20th pro success.
Several boxing experts believed Parker, thirty-one, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-bout career.
The Champion Claims Win in Dull Encounter
Buatsi's progress has plateaued in recent times through promotional disputes and long spells of inactivity.
Earlier forecast as the rising talent of British boxing, he now is positioned trying to achieve expectations - maybe in what appears to be a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to take risks in a tentative initial rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was participating in his second fight at the higher weight class.
By the fight's midpoint, the underdog had kept it close, making life awkward for Buatsi, who worked behind a protective stance to narrowly win the cleaner periods.
The spectators' acceptance diminished amid regular grabbing, with the challenger slipping to the canvas multiple occasions during grappling.
Parker ended stronger, but multiple periods were hard to judge. Although, former world champion Carl Frampton - working with Dazn - had it particularly wide for Parker, awarding Buatsi just only one stanza.
The victor progresses, but with the presence of heavy hitter David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Tribute Motivates All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Bradley Rea by close verdict in a terrific local rivalry battle to secure the continental title.
The arena fell silent for a deeply poignant tribute ahead of the contest as 10 bells tolled in remembrance of Manchester's own Ricky Hatton, who passed away aged 46 in September.
It was the first major televised fight night in the city since the passing of Hatton. As the last bell faded, the quiet gave way to a shout of "only one Ricky Hatton".
The competition inside the ropes matched the feeling. The eventual winner was knocked down by a left hook directly to the chin in the initial stage, getting up unsteadily to his position on the eight count.
But the Manchester United-red attire of Arthur soon came forward again. From the other corner, the opponent - in rival City blue - was damaged early, heavy swelling developing under his eye as the fighters traded powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity rarely dropped over 12 rounds.
Arthur barely secured the verdict with official scores of 114-114, 115-113 and wider gap, but each competitor were persistent and brave, exactly what their inspiration the legend stood for.
