UK light heavyweight Buatsi secured a victory yet unimpressive start to his career under new promoters with a points victory over Zach Parker in the Manchester arena.
The Olympic medal winner's activity level likely gained him a judges' verdict in a tight ten-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful clean blows in a fight where the techniques failed to mesh, with excessive holding marring the contest.
The scoring judges had it 96-94 for to Buatsi, with the remaining official a even score.
"It wasn't my greatest showing but what do champions do? They succeed," Buatsi said in the ringside as he was met by disapproval from the spectators.
The British fighter got back to winning after his first professional defeat - an thrilling contest with his previous opponent in last winter - to secure a 20th pro success.
Several boxing experts thought the challenger, 31, deserved the victory but the British boxer suffered the second loss of his 28-fight professional journey.
The Champion Earns Victory in Dull Affair
His career development has stalled in recent times through management issues and extended periods of inactivity.
Previously predicted as the next star of the British fight scene, he now stands trying to fulfil that early promise - perhaps in what seems like a final roll of the dice - under new promotional backing.
He opened tentatively, with both competitors willing to take risks in a cagey initial rounds.
Parker, whose single earlier setback came at super middleweight against his former opponent in 2022 after damaging his hand mid-fight, was participating in his second fight at light heavyweight.
By the halfway stage, the underdog had kept it close, making life awkward for the favorite, who utilized a solid defense to narrowly win the better stanzas.
The spectators' acceptance diminished because of constant clinching, with Parker going down various instances during grappling.
Parker ended stronger, but many rounds were hard to judge. However, previous titleholder the boxing analyst - commentating on the broadcast network - had it particularly wide for Parker, awarding Buatsi just one round.
Buatsi moves on, but with the presence of hard hitter David Benavidez, and Russian star Dmitry Bivol dominating the weight class, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Battle
In the secondary fight, Lyndon Arthur beat Rea by divided decision in a terrific local rivalry fight to capture the European light-heavyweight title.
The venue grew hushed for a extremely emotional homage before the fight as ten bells rang in remembrance of Manchester's own Ricky Hatton, who passed away at age 46 in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the concluding sound ended, the quiet became a shout of "there's just one Ricky Hatton".
The action within the ring matched the feeling. Arthur was floored by a significant blow squarely on the face in the initial stage, standing uncertainly to his feet on the referee's count.
But the traditional red shorts of the fighter soon pressed ahead again. From the other corner, the opponent - in opposing blue - was damaged soon, heavy swelling forming under his orbital area as the pair exchanged powerful shots.
Rea, twenty-seven, landed power punches but the champion, thirty-four, fought fire with fire with effective uppercuts as the pace rarely dropped over twelve rounds.
Arthur barely secured the result with scoring tallies of draw, narrow lead and wider gap, but both fighters were persistent and full of heart, all the qualities their hero the legend embodied.
