UK light-heavyweight Buatsi earned a win yet unimpressive start to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic bronze medallist's punch output likely gained him a split decision in a close ten-round bout at the Co-op Live Arena.
But the challenger found success, connecting with powerful clean blows in a contest where the styles failed to mesh, with frequent clinching marring the action.
The scoring judges had it 96-94 in favor to the winner, with the final judge a 95-95.
"It wasn't my finest display but how do champions respond? They prevail," the victor stated in the ringside as he was met by boos from the audience.
The British fighter bounced back after his initial pro loss - an memorable fight 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 defeat of his 28-match career.
The Champion Claims Triumph in Uneventful Match
Buatsi's progress has plateaued in recent times through management issues and long spells of inactivity.
Earlier forecast as the rising talent of UK boxing, he now stands trying to achieve expectations - maybe in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with neither fighter ready to take risks in a tentative early stages.
The challenger, whose sole prior loss came at super-middleweight against John Ryder in 2022 after damaging his hand mid-fight, was making just his second fight at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for Buatsi, who worked behind a solid defense to narrowly win the better rounds.
The crowd's patience diminished because of constant clinching, with Parker falling to the floor various instances during close exchanges.
Parker closed well, but many rounds were hard to judge. Nevertheless, previous titleholder the boxing analyst - working with Dazn - had it particularly wide for the challenger, scoring for Buatsi just only one stanza.
Buatsi progresses, but with the likes of power puncher David Benavidez, and Russian champion Bivol dominating the weight class, the journey to titles - judging by this showing - still looks steep.
Hatton Tribute Fuels Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by divided decision in a terrific all-Manchester battle to win the continental belt.
The stadium fell silent for a profoundly moving tribute ahead of the contest as a bell ceremony sounded in remembrance of Manchester's own Hatton, who passed away aged 46 in last month.
It was the initial significant broadcast match card in the location since the passing of Hatton. As the last bell disappeared, the stillness transitioned to a shout of "only one Ricky Hatton".
The competition inside the ropes reflected the feeling. Arthur was sent to the canvas by a left hook directly to the jaw in the initial stage, rising shakily to his footing on the eight count.
But the red-colored equipment of Arthur soon pressed ahead again. Across the ring, Rea - in competitive blue - was damaged quickly, heavy swelling forming under his orbital area as the fighters exchanged punishing blows.
The challenger, twenty-seven, delivered effective strikes but Arthur, thirty-four, fought fire with fire with effective uppercuts as the intensity seldom decreased over 12 rounds.
Arthur narrowly won the decision with official scores of 114-114, narrow lead and clearer margin, but each competitor were relentless and courageous, everything their hero the legend represented.
