UK light-heavyweight Buatsi made a winning yet unimpressive beginning to life under new promoters with a unanimous decision over Zach Parker in Manchester.
The Olympic bronze medallist's work rate likely gained him a majority decision in a tight 10-round contest at the Manchester venue.
But Parker landed significant shots, connecting with powerful single shots in a fight where the styles never quite clicked, with frequent clinching disrupting the fight.
The scoring judges scored it 96-94 for to Buatsi, with the final judge a 95-95.
"It wasn't my best performance but what do champions do? They prevail," Buatsi said in the arena as he was greeted with boos from the audience.
The British fighter got back to winning after his first professional defeat - an memorable fight with his previous opponent in last winter - to claim a 20th pro success.
Several boxing experts felt Parker, thirty-one, should have been awarded the victory but the Derbyshire fighter experienced the second setback of his 28-bout career.
The Champion Claims Triumph in Uneventful Affair
The fighter's advancement has slowed in recent years through promotional disputes and long spells of inactivity.
Once tipped as the next star of British boxing, he now finds himself trying to realize his potential - maybe in what appears to be a ultimate opportunity - under recent support.
He began cautiously, with the two boxers prepared to overcommit in a calculated early stages.
The challenger, whose only previous defeat came at super middleweight against his former opponent in 2022 after breaking his hand mid-fight, was participating in his second appearance at the higher weight class.
By the middle rounds, Parker had made it competitive, causing problems for the favorite, who utilized a protective stance to barely take the cleaner rounds.
The spectators' acceptance wore thin amid frequent holding, with Parker slipping to the canvas multiple occasions during close exchanges.
The underdog closed well, but several stanzas were difficult to score. Although, former world champion the boxing analyst - commentating on the broadcast network - had it particularly wide for the challenger, scoring for Buatsi just a single round.
Buatsi progresses, but with the likes of heavy hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Motivates All-Manchester Fight
In the co-main event, Lyndon Arthur overcame Rea by close verdict in a outstanding all-Manchester contest to secure the European light heavyweight title.
The venue fell silent for a profoundly moving homage prior to the bout as a bell ceremony tolled in memory of Manchester's own Hatton, who succumbed aged 46 in last month.
It was the initial significant broadcast fight night in the location since Hatton's death. As the final chime faded, the silence became a shout of "only one Ricky Hatton".
The fighting within the ring reflected the feeling. The eventual winner was knocked down by a left hook directly to the jaw in the initial stage, getting up unsteadily to his footing on the referee's count.
But the red-colored shorts of Arthur soon advanced again. From the other corner, the opponent - in rival City blue - was injured quickly, significant bruising forming under his orbital area as the duo exchanged powerful shots.
The challenger, 27, connected with strong blows but Arthur, 34, fought fire with fire with effective uppercuts as the action rarely dropped over twelve rounds.
The victor edged the decision with scoring tallies of 114-114, close margin and wider gap, but both fighters were persistent and brave, everything their idol Hatton stood for.
