UK light heavyweight Buatsi secured a victory yet disappointing start to life under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic bronze medallist's activity level likely gained him a split decision in a close 10-round bout at the boxing arena.
But the challenger had his moments, connecting with powerful clean blows in a match where the styles didn't complement each other, with frequent clinching spoiling the action.
Two judges scored it 96-94 for to the winner, with the third a 95-95.
"It wasn't my best showing but what defines champions? They prevail," the victor commented in the ringside as he was met by boos from the crowd.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to claim a 20th pro success.
Various analysts thought Parker, 31, merited the win but the British boxer suffered the second defeat of his 28-match professional journey.
The Champion Earns Triumph in Dull Encounter
Buatsi's progress has slowed in recent years through management issues and long spells of lack of fights.
Earlier forecast as the rising talent of British boxing, he now stands trying to achieve expectations - perhaps in what appears to be a last chance - under new promotional backing.
He started carefully, with neither fighter willing to overcommit in a calculated initial rounds.
The challenger, whose sole prior loss came at the lower weight class against his former opponent in 2022 after damaging his hand in the contest, was competing in only his second appearance at light heavyweight.
By the fight's midpoint, Parker had stayed in contention, creating difficulties for the favorite, who operated with a tight guard to barely take the better periods.
The crowd's patience wore thin because of regular grabbing, with the challenger slipping to the canvas multiple occasions during clinches.
The underdog closed well, but multiple periods were hard to judge. Nevertheless, ex-champion the boxing analyst - commentating on Dazn - had it significantly in favor for the challenger, giving Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian star Bivol ruling the division, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Fight
In the supporting bout, Lyndon Arthur overcame Bradley Rea by close verdict in a outstanding Manchester vs Manchester fight to win the European light-heavyweight belt.
The arena fell silent for a profoundly moving memorial prior to the bout as ten bells rang in honor of Manchester's own Hatton, who passed away aged 46 in last month.
It was the premier televised fight night in the city since Hatton's passing. As the final chime ended, the stillness gave way to a shout of "only one Ricky Hatton".
The action within the ring matched the feeling. Arthur was knocked down by a significant blow squarely on the face in the second round, getting up unsteadily to his feet on the referee's count.
But the Manchester United-red attire of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was injured quickly, noticeable damage appearing under his face as the duo exchanged punishing blows.
The challenger, 27, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the result with judges scorecards of 114-114, close margin and 115-112, but both fighters were persistent and brave, exactly what their idol Hatton stood for.
