UK light-heavyweight Buatsi earned a win yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's activity level seemingly secured him a judges' verdict in a tight 10-round contest at the Manchester venue.
But Parker had his moments, connecting with powerful single shots in a fight where the styles didn't complement each other, with constant grabbing spoiling the action.
Two judges had it 96-94 in favor to Buatsi, with the remaining official a even score.
"It wasn't my best performance but what defines champions? They prevail," the victor stated in the ringside as he was greeted with disapproval from the audience.
The Londoner returned to winning ways after his first professional defeat - an thrilling contest with Callum Smith in last winter - to secure a 20th pro success.
Some ringside observers believed Parker, thirty-one, merited the win but the contender suffered the second setback of his 28-bout career.
The Champion Secures Win in Slow Match
His career development has slowed in recent years through contract problems and long spells of inactivity.
Once tipped as the rising talent of the British fight scene, he now is positioned trying to fulfil that early promise - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers willing to be aggressive in a cagey early stages.
Parker, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand mid-fight, was participating in his second bout at the higher weight class.
By the middle rounds, the underdog had kept it close, making life awkward for Buatsi, who utilized a protective stance to edge the more effective stanzas.
The spectators' acceptance decreased amid frequent holding, with the challenger falling to the floor several times during grappling.
Parker closed well, but several stanzas were difficult to score. Although, ex-champion the boxing analyst - working with Dazn - had it significantly in favor for Parker, scoring for Buatsi just a single round.
The victor progresses, but with the caliber of power puncher David Benavidez, and Russian champion Dmitry Bivol ruling the division, the journey to titles - based on this performance - still appears challenging.
Hatton Homage Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Bradley Rea by divided decision in a outstanding local rivalry battle to win the European light heavyweight championship.
The stadium fell silent for a profoundly moving memorial ahead of the contest as 10 bells rang in memory of local hero Hatton, who passed away at age 46 in September.
It was the premier televised boxing event in the city since Hatton's death. As the last bell faded, the stillness transitioned to a roar of "only one Hatton".
The competition within the ring reflected the sentiment. Arthur was floored by a significant blow squarely on the face in the early round, getting up unsteadily to his position on the eight count.
But the traditional red equipment of the fighter soon pressed ahead again. On the opposite side, Rea - in rival City blue - was injured early, significant bruising appearing under his face as the pair traded hard punches.
Rea, 27, delivered effective strikes but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace hardly diminished over 12 rounds.
Arthur barely secured the result with official scores of 114-114, 115-113 and clearer margin, but both fighters were relentless and courageous, everything their inspiration the legend represented.
