UK light heavyweight Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level seemingly secured him a majority decision in a competitive 10-round bout at the boxing arena.
But Parker landed significant shots, connecting with powerful individual punches in a fight where the techniques failed to mesh, with excessive holding disrupting the fight.
Two judges judged it 96-94 for to the winner, with the final judge a 95-95.
"It wasn't my finest display but what defines champions? They succeed," Buatsi stated in the arena as he was faced boos from the spectators.
The British fighter bounced back after his initial pro loss - an memorable fight with his previous opponent in February - to claim a twentieth professional win.
Several boxing experts felt Parker, 31, should have been awarded the win but the Derbyshire fighter suffered the second setback of his 28-bout professional journey.
Buatsi Secures Win in Slow Affair
Buatsi's progress has slowed in the past few years through management issues and extended periods of inactivity.
Once tipped as the future of UK boxing, he now is positioned trying to fulfil that early promise - perhaps in what feels like a ultimate opportunity - under new promotional backing.
He opened tentatively, with both competitors prepared to overcommit in a calculated opening few rounds.
The challenger, whose single earlier setback came at the lower weight class against John Ryder in 2022 after damaging his hand in the contest, was making just his second fight at light heavyweight.
By the halfway stage, Parker had stayed in contention, causing problems for the favorite, who utilized a protective stance to edge the better rounds.
The crowd's patience decreased amid constant clinching, with Parker going down several times during clinches.
Parker closed well, but multiple periods were hard to judge. However, previous titleholder Carl Frampton - providing analysis for the broadcast network - had it particularly wide for Parker, scoring for Buatsi just only one stanza.
The victor advances, but with the likes of hard hitter Benavidez, and Russian champion Bivol leading the category, the road to world glory - based on this performance - still looks steep.
Ricky Hatton Homage Motivates Manchester Derby Contest
In the secondary fight, Arthur overcame Rea by divided decision in a terrific all-Manchester fight to capture the European light-heavyweight belt.
The venue grew hushed for a profoundly moving memorial before the fight as a bell ceremony sounded in honor of local hero Ricky Hatton, who passed away aged 46 in September.
It was the first major televised match card in the location since Hatton's death. As the final chime faded, the quiet became a chant of "there's just one Ricky Hatton".
The fighting inside the ropes reflected the feeling. Arthur was knocked down by a left hook directly to the face in the initial stage, standing uncertainly to his footing on the count of eight.
But the traditional red attire of the fighter soon pressed ahead again. From the other corner, Rea - in opposing blue - was marked up quickly, noticeable damage developing under his eye as the duo landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, 34, matched the intensity with effective uppercuts as the intensity rarely dropped over twelve rounds.
The victor barely secured the decision with official scores of 114-114, 115-113 and wider gap, but both fighters were persistent and courageous, everything their inspiration the legend stood for.
