British light heavyweight Buatsi secured a victory yet disappointing beginning to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a close 10-round bout at the boxing arena.
But Parker had his moments, landing some telling individual punches in a contest where the techniques never quite clicked, with constant grabbing disrupting the contest.
Two judges judged it 96-94 for to the winner, with the third a even score.
"It wasn't my greatest display but what defines champions? They succeed," Buatsi said in the ringside as he was faced disapproval from the crowd.
The British fighter bounced back after his maiden career setback - an epic battle with his previous opponent in February - to secure a 20th pro success.
Several boxing experts believed the challenger, 31, deserved the victory but the British boxer experienced the second loss of his 28-fight career.
Buatsi Claims Victory in Slow Encounter
His career development has slowed in the past few years through promotional disputes and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now is positioned trying to achieve expectations - perhaps in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers prepared to take risks in a calculated early stages.
Parker, whose sole prior loss came at super-middleweight against John Ryder in two years ago after breaking his hand mid-fight, was competing in only his second appearance at light-heavyweight.
By the middle rounds, Parker had kept it close, creating difficulties for the favorite, who operated with a solid defense to edge the cleaner rounds.
The spectators' acceptance diminished because of frequent holding, with the challenger slipping to the canvas various instances during clinches.
The underdog ended stronger, but several stanzas were hard to judge. Nevertheless, former world champion the boxing analyst - providing analysis for Dazn - had it strongly leaning for the challenger, awarding Buatsi just one round.
Buatsi moves on, but with the likes of hard hitter Benavidez, and Eastern European fighter Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still seems difficult.
Hatton Tribute Fuels All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Bradley Rea by divided decision in a terrific all-Manchester contest to win the European light heavyweight championship.
The stadium became quiet for a extremely emotional tribute prior to the bout as a bell ceremony rang in memory of local hero Ricky Hatton, who succumbed aged 46 in September.
It was the premier televised match card in the city since Hatton's death. As the final chime ended, the silence transitioned to a roar of "there's only one Hatton".
The action within the ring matched the sentiment. Arthur was sent to the canvas by a left hook directly to the chin in the early round, standing uncertainly to his footing on the eight count.
But the Manchester United-red equipment of Arthur soon advanced again. From the other corner, the opponent - in opposing blue - was marked up soon, significant bruising appearing under his eye as the duo landed punishing blows.
The challenger, 27, landed power punches but Arthur, thirty-four, matched the intensity with stinging uppercuts as the action seldom decreased over twelve rounds.
Arthur barely secured the decision with judges scorecards of draw, close margin and clearer margin, but each competitor were relentless and courageous, everything their hero Hatton represented.
