British light-heavyweight Buatsi made a winning yet unimpressive debut to his career under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate likely gained him a majority decision in a close ten-round fight at the Co-op Live Arena.
But Parker found success, landing some telling single shots in a contest where the techniques never quite clicked, with constant grabbing marring the fight.
The officials scored it 96-94 to Buatsi, with the remaining official a 95-95.
"It wasn't my greatest showing but how do champions respond? They prevail," Buatsi commented in the ringside as he was met by disapproval from the audience.
The British fighter returned to winning ways after his first professional defeat - an epic battle with Callum Smith in February - to earn a 20th career victory.
Various analysts thought Parker, thirty-one, merited the win but the contender suffered the second defeat of his 28-match professional journey.
The Champion Claims Triumph in Dull Encounter
The fighter's advancement has stalled in recent years through management issues and long spells of lack of fights.
Previously predicted as the next star of British boxing, he now finds himself trying to fulfil that early promise - maybe in what appears to be a last chance - under fresh management.
He began cautiously, with neither fighter prepared to be aggressive in a tentative opening few rounds.
Parker, whose sole prior loss came at the lower weight class against his former opponent in 2022 after suffering a hand injury mid-fight, was participating in his second fight at light-heavyweight.
By the halfway stage, the underdog had stayed in contention, causing problems for Buatsi, who worked behind a protective stance to barely take the more effective rounds.
The crowd's patience wore thin amid constant clinching, with the challenger slipping to the canvas multiple occasions during clinches.
Parker ended stronger, but several stanzas were difficult to score. Although, former world champion the boxing analyst - providing analysis for the broadcast network - had it particularly wide for the challenger, giving Buatsi just one round.
The victor moves on, but with the likes of hard hitter David Benavidez, and Russian champion Bivol leading the category, the path to championship success - on this evidence - still appears challenging.
Hatton Homage Motivates Manchester Derby Fight
In the co-main event, Lyndon Arthur defeated Bradley Rea by divided decision in a terrific Manchester vs Manchester contest to capture the continental belt.
The venue grew hushed for a extremely emotional homage ahead of the contest as a bell ceremony rang in honor of the city's native Ricky Hatton, who died 46 years old in recently.
It was the initial significant broadcast fight night in the urban center since Hatton's death. As the final chime disappeared, the stillness became a roar of "there's only one Hatton".
The competition during the bout equaled the emotion. The eventual winner was knocked down by a left hook flush on the face in the early round, rising shakily to his feet on the referee's count.
But the Manchester United-red equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was injured soon, heavy swelling developing under his face as the duo traded punishing blows.
The challenger, 27, delivered effective strikes but Arthur, 34, matched the intensity with powerful upward punches as the intensity rarely dropped over the full distance.
Arthur barely secured the verdict with official scores of draw, close margin and 115-112, but both fighters were determined and full of heart, all the qualities their hero the legend represented.
