UK light-heavyweight Buatsi earned a win yet underwhelming start to life under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a split decision in a competitive ten-round contest at the Co-op Live Arena.
But Parker found success, connecting with powerful individual punches in a match where the techniques didn't complement each other, with excessive holding spoiling the action.
Two judges scored it 96-94 to the winner, with the remaining official a even score.
"It wasn't my best display but how do champions respond? They succeed," Buatsi commented in the ring as he was greeted with negative reactions from the audience.
The Londoner got back to winning after his first professional defeat - an memorable fight with his previous opponent in February - to earn a twentieth professional win.
Various analysts believed Parker, 31, deserved the decision but the Derbyshire fighter experienced the second defeat of his 28-bout career.
The Champion Secures Win in Uneventful Affair
The fighter's advancement has stalled in the past few years through contract problems and extended periods of inactivity.
Once tipped as the rising talent of British boxing, he now finds himself trying to achieve expectations - possibly in what appears to be a ultimate opportunity - under new promotional backing.
He started carefully, with the two boxers prepared to take risks in a tentative opening few rounds.
The challenger, whose single earlier setback 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 halfway stage, the underdog had made it competitive, creating difficulties for the favorite, who operated with a protective stance to barely take the more effective rounds.
The audience's tolerance wore thin during regular grabbing, with Parker falling to the floor various instances during clinches.
The underdog ended stronger, but several stanzas were hard to judge. Although, ex-champion the boxing analyst - working with the broadcast network - had it particularly wide for Parker, awarding Buatsi just a single round.
The victor advances, but with the presence of power puncher David Benavidez, and Russian star Dmitry Bivol ruling the division, the journey to titles - based on this performance - still looks steep.
Hatton Tribute Fuels All-Manchester Contest
In the secondary fight, Arthur beat Bradley Rea by split-decision in a outstanding Manchester vs Manchester contest to secure the European light-heavyweight championship.
The stadium fell silent for a profoundly moving homage prior to the bout as a bell ceremony rang in memory of the city's native Ricky Hatton, who died at age 46 in September.
It was the first major televised match card in the city since Hatton's passing. As the concluding sound faded, the silence gave way to a shout of "only one Ricky Hatton".
The action during the bout matched the feeling. Arthur was sent to the canvas by a powerful punch directly to the face in the second round, getting up unsteadily to his position on the eight count.
But the red-colored shorts of the fighter soon pressed ahead again. Across the ring, the opponent - in rival City blue - was marked up quickly, noticeable damage developing under his orbital area as the pair landed powerful shots.
Rea, 27, landed power punches but the champion, thirty-four, responded in kind with stinging uppercuts as the action seldom decreased over the full distance.
The victor barely secured the decision with official scores of 114-114, narrow lead and wider gap, but the two athletes were determined and full of heart, exactly what their hero Hatton embodied.
