UK light heavyweight Buatsi secured a victory yet disappointing beginning to his career under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a split decision in a close ten-round fight at the boxing arena.
But Parker landed significant shots, connecting with powerful individual punches in a match where the techniques didn't complement each other, with excessive holding disrupting the action.
Two judges scored it 96-94 in favor to the winner, with the third a even score.
"It wasn't my greatest showing but what defines champions? They succeed," Buatsi said in the arena as he was met by disapproval from the crowd.
The British fighter got back to winning after his maiden career setback - an epic battle with Callum Smith in last winter - to earn a twentieth professional win.
Several boxing experts thought Parker, thirty-one, merited the victory but the contender experienced the second defeat of his 28-match career.
Buatsi Claims Victory in Uneventful Encounter
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the future of UK boxing, he now is positioned trying to achieve expectations - possibly in what appears to be a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a cagey early stages.
Parker, whose sole prior loss came at super middleweight against his former opponent in two years ago after damaging his hand mid-fight, was participating in his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, creating difficulties for Buatsi, who utilized a protective stance to barely take the cleaner stanzas.
The crowd's patience decreased during frequent holding, with the challenger slipping to the canvas various instances during clinches.
The underdog ended stronger, but several stanzas were difficult to score. Nevertheless, ex-champion Carl Frampton - commentating on Dazn - had it strongly leaning for Parker, awarding Buatsi just a single round.
The victor progresses, but with the presence of heavy hitter Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - based on this performance - still appears challenging.
Hatton Memorial Inspires All-Manchester Contest
In the co-main event, Lyndon Arthur defeated Rea by close verdict in a outstanding Manchester vs Manchester battle to win the European light-heavyweight championship.
The venue became quiet for a deeply poignant tribute before the fight as 10 bells sounded in memory of local hero Hatton, who passed away aged 46 in September.
It was the initial significant broadcast match card in the city since the passing of Hatton. As the last bell disappeared, the silence gave way to a roar of "only one Hatton".
The competition during the bout reflected the sentiment. Arthur was sent to the canvas by a left hook directly to the chin in the second round, getting up unsteadily to his position on the referee's count.
But the traditional red attire of Arthur soon pressed ahead again. From the other corner, Rea - in rival City blue - was damaged quickly, significant bruising developing under his face as the fighters landed punishing blows.
The challenger, 27, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the intensity rarely dropped over twelve rounds.
Arthur barely secured the decision with official scores of 114-114, close margin and 115-112, but both fighters were relentless and brave, all the qualities their hero Hatton embodied.
